def METHOD_NAME(self) -> Set[Dim]:
    """
    :return: set of dim tags. in all high-level code, the order of dims is irrelevant.
      The order must not play a role
      (RETURNN principles: https://github.com/rwth-i6/returnn/wiki/RETURNN-principles).
      Note that we do not include any implicit dims here.
      Also see :func:`verify_out_shape` and https://github.com/rwth-i6/returnn/issues/1153.
    """
    return set(self._dims)