Synnefo

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from django.db.models import Manager

from django.db.models.query import QuerySet

class ProtectedDeleteManager(Manager):

    """Manager for protecting Backend deletion.

    Call Backend delete() method in order to prevent deletion

    of Backends that host non-deleted VirtualMachines.

    """

    def get_query_set(self):

        return BackendQuerySet(self.model, using=self._db)

class BackendQuerySet(QuerySet):

    def delete(self):

        for backend in self._clone():

            backend.delete()