docs: def move_to_collection(self, source_collection, destination_collection):
          """Move entity from source to destination collection."""
          # Remove from collection.
          self.collections.remove(source_collection)  # pylint: disable=no-member
          source_collection.data.remove(*self.data.all())  # pylint: disable=no-member
  
          # Add to collection.
          self.collections.add(destination_collection)  # pylint: disable=no-member
          destination_collection.data.add(*self.data.all())