content: # Copyright (c) 2009, Peter Sagerson
  # All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions are met:
  #
  # - Redistributions of source code must retain the above copyright notice, this
  # list of conditions and the following disclaimer.
  #
  # - Redistributions in binary form must reproduce the above copyright notice,
  # this list of conditions and the following disclaimer in the documentation
  # and/or other materials provided with the distribution.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  # DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  # SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  from users.models import Group
  
  
  # Copied from django_auth_ldap.backend._LDAPUser and modified to support our
  # custom Group model.
  def _mirror_groups(self):
      """
      Mirrors the user's LDAP groups in the Django database and updates the
      user's membership.
      """
      target_group_names = frozenset(self._get_groups().get_group_names())
      current_group_names = frozenset(
          self._user.groups.values_list("name", flat=True).iterator()
      )
  
      # These were normalized to sets above.
      MIRROR_GROUPS_EXCEPT = self.settings.MIRROR_GROUPS_EXCEPT
      MIRROR_GROUPS = self.settings.MIRROR_GROUPS
  
      # If the settings are white- or black-listing groups, we'll update
      # target_group_names such that we won't modify the membership of groups
      # beyond our purview.
      if isinstance(MIRROR_GROUPS_EXCEPT, (set, frozenset)):
          target_group_names = (target_group_names - MIRROR_GROUPS_EXCEPT) | (
              current_group_names & MIRROR_GROUPS_EXCEPT
          )
      elif isinstance(MIRROR_GROUPS, (set, frozenset)):
          target_group_names = (target_group_names & MIRROR_GROUPS) | (
              current_group_names - MIRROR_GROUPS
          )
  
      if target_group_names != current_group_names:
          existing_groups = list(
              Group.objects.filter(name__in=target_group_names).iterator()
          )
          existing_group_names = frozenset(group.name for group in existing_groups)
  
          new_groups = [
              Group.objects.get_or_create(name=name)[0]
              for name in target_group_names
              if name not in existing_group_names
          ]
  
          self._user.groups.set(existing_groups + new_groups)
  