root / lib / qlang.py @ 3f2f55bb
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# Copyright (C) 2010, 2011 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module for a simple query language
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A query filter is always a list. The first item in the list is the operator
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(e.g. C{[OP_AND, ...]}), while the other items depend on the operator. For
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logic operators (e.g. L{OP_AND}, L{OP_OR}), they are subfilters whose results
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are combined. Unary operators take exactly one other item (e.g. a subfilter for
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L{OP_NOT} and a field name for L{OP_TRUE}). Binary operators take exactly two
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operands, usually a field name and a value to compare against. Filters are
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converted to callable functions by L{query._CompileFilter}.
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"""
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import re |
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import string # pylint: disable-msg=W0402 |
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import pyparsing as pyp |
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from ganeti import errors |
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from ganeti import netutils |
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# Logic operators with one or more operands, each of which is a filter on its
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# own
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OP_OR = "|"
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OP_AND = "&"
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# Unary operators with exactly one operand
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OP_NOT = "!"
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OP_TRUE = "?"
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# Binary operators with exactly two operands, the field name and an
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# operator-specific value
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OP_EQUAL = "="
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OP_NOT_EQUAL = "!="
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OP_REGEXP = "=~"
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OP_CONTAINS = "=[]"
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#: Characters used for detecting user-written filters (see L{MaybeFilter})
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FILTER_DETECTION_CHARS = frozenset("()=/!~" + string.whitespace) |
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def MakeSimpleFilter(namefield, values): |
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"""Builds simple a filter.
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@param namefield: Name of field containing item name
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@param values: List of names
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"""
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if values:
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return [OP_OR] + [[OP_EQUAL, namefield, i] for i in values] |
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return None |
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def _ConvertLogicOp(op): |
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"""Creates parsing action function for logic operator.
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@type op: string
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@param op: Operator for data structure, e.g. L{OP_AND}
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"""
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def fn(toks): |
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"""Converts parser tokens to query operator structure.
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@rtype: list
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@return: Query operator structure, e.g. C{[OP_AND, ["=", "foo", "bar"]]}
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"""
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operands = toks[0]
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if len(operands) == 1: |
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return operands[0] |
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# Build query operator structure
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return [[op] + operands.asList()]
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return fn
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_KNOWN_REGEXP_DELIM = "/#^|"
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_KNOWN_REGEXP_FLAGS = frozenset("si") |
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def _ConvertRegexpValue(_, loc, toks): |
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"""Regular expression value for condition.
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"""
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(regexp, flags) = toks[0]
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# Ensure only whitelisted flags are used
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unknown_flags = (frozenset(flags) - _KNOWN_REGEXP_FLAGS)
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if unknown_flags:
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raise pyp.ParseFatalException("Unknown regular expression flags: '%s'" % |
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"".join(unknown_flags), loc)
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if flags:
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re_flags = "(?%s)" % "".join(sorted(flags)) |
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else:
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re_flags = ""
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re_cond = re_flags + regexp |
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# Test if valid
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try:
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re.compile(re_cond) |
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except re.error, err:
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raise pyp.ParseFatalException("Invalid regular expression (%s)" % err, loc) |
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return [re_cond]
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def BuildFilterParser(): |
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"""Builds a parser for query filter strings.
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@rtype: pyparsing.ParserElement
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"""
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field_name = pyp.Word(pyp.alphas, pyp.alphanums + "_/.")
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# Integer
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num_sign = pyp.Word("-+", exact=1) |
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number = pyp.Combine(pyp.Optional(num_sign) + pyp.Word(pyp.nums)) |
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number.setParseAction(lambda toks: int(toks[0])) |
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# Right-hand-side value
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rval = (number | pyp.quotedString.setParseAction(pyp.removeQuotes)) |
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# Boolean condition
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bool_cond = field_name.copy() |
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bool_cond.setParseAction(lambda (fname, ): [[OP_TRUE, fname]])
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# Simple binary conditions
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binopstbl = { |
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"==": OP_EQUAL,
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"!=": OP_NOT_EQUAL,
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} |
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binary_cond = (field_name + pyp.oneOf(binopstbl.keys()) + rval) |
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binary_cond.setParseAction(lambda (lhs, op, rhs): [[binopstbl[op], lhs, rhs]])
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# "in" condition
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in_cond = (rval + pyp.Suppress("in") + field_name)
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in_cond.setParseAction(lambda (value, field): [[OP_CONTAINS, field, value]])
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# "not in" condition
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not_in_cond = (rval + pyp.Suppress("not") + pyp.Suppress("in") + field_name) |
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not_in_cond.setParseAction(lambda (value, field): [[OP_NOT, [OP_CONTAINS,
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field, value]]]) |
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# Regular expression, e.g. m/foobar/i
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regexp_val = pyp.Group(pyp.Optional("m").suppress() +
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pyp.MatchFirst([pyp.QuotedString(i, escChar="\\")
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for i in _KNOWN_REGEXP_DELIM]) + |
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pyp.Optional(pyp.Word(pyp.alphas), default=""))
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regexp_val.setParseAction(_ConvertRegexpValue) |
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regexp_cond = (field_name + pyp.Suppress("=~") + regexp_val)
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regexp_cond.setParseAction(lambda (field, value): [[OP_REGEXP, field, value]])
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not_regexp_cond = (field_name + pyp.Suppress("!~") + regexp_val)
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not_regexp_cond.setParseAction(lambda (field, value):
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[[OP_NOT, [OP_REGEXP, field, value]]]) |
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# All possible conditions
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condition = (binary_cond ^ bool_cond ^ |
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in_cond ^ not_in_cond ^ |
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regexp_cond ^ not_regexp_cond) |
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# Associativity operators
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filter_expr = pyp.operatorPrecedence(condition, [ |
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(pyp.Keyword("not").suppress(), 1, pyp.opAssoc.RIGHT, |
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lambda toks: [[OP_NOT, toks[0][0]]]), |
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(pyp.Keyword("and").suppress(), 2, pyp.opAssoc.LEFT, |
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_ConvertLogicOp(OP_AND)), |
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(pyp.Keyword("or").suppress(), 2, pyp.opAssoc.LEFT, |
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_ConvertLogicOp(OP_OR)), |
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]) |
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parser = pyp.StringStart() + filter_expr + pyp.StringEnd() |
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parser.parseWithTabs() |
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# Originally C{parser.validate} was called here, but there seems to be some
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# issue causing it to fail whenever the "not" operator is included above.
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return parser
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def ParseFilter(text, parser=None): |
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"""Parses a query filter.
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@type text: string
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@param text: Query filter
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@type parser: pyparsing.ParserElement
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@param parser: Pyparsing object
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@rtype: list
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"""
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if parser is None: |
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parser = BuildFilterParser() |
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try:
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return parser.parseString(text)[0] |
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except pyp.ParseBaseException, err:
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raise errors.QueryFilterParseError("Failed to parse query filter" |
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" '%s': %s" % (text, err), err)
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def MaybeFilter(text): |
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"""Try to determine if a string is a filter or a name.
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If in doubt, this function treats a text as a name.
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@type text: string
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@param text: String to be examined
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@rtype: bool
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"""
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# Quick check for punctuation and whitespace
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if frozenset(text) & FILTER_DETECTION_CHARS: |
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return True |
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try:
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netutils.Hostname.GetNormalizedName(text) |
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except errors.OpPrereqError:
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# Not a valid hostname, treat as filter
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return True |
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# Most probably a name
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return False |