code: def _partition_index_names(provisioned_index_names, index_names):
      '''Returns 3 disjoint sets of indexes: existing, to be created, and to be deleted.'''
      existing_index_names = set()
      new_index_names = set()
      for name in index_names:
          if name in provisioned_index_names:
              existing_index_names.add(name)
          else:
              new_index_names.add(name)
      index_names_to_be_deleted = provisioned_index_names - existing_index_names
      return existing_index_names, new_index_names, index_names_to_be_deletef _partition_index_names(provisioned_index_names, index_names):
      '''Returns 3 disjoint sets of indexes: existing, to be created, and to be deleted.'''
      existing_index_names = set()
      new_index_names = set()
      for name in index_names:
          if name in provisioned_index_names:
              existing_index_names.add(name)
          else:
              new_index_names.add(name)
      index_names_to_be_deleted = provisioned_index_names - existing_index_names
      return existing_index_names, new_index_names, index_names_to_be_deleted
docs: Returns 3 disjoint sets of indexes: existing, to be created, and to be deleted.