docs: def create_child_ref(self, transform_path, child_id=None):
          """
          Creates a new child TransformRef with transform_path specified.
          :param transform_path:
          :param child_id:
          :return: TransformRef child
          """
          transform_ref = TransformRef(transform_path, child_id)
          self.add_child_ref(transform_ref)
          return transform_ref