Adds a copy of Graph with the specified set of tags.

def add_graph_copy(self, graph, tags=None):
    """Adds a copy of Graph with the specified set of tags."""
    with graph.as_default():
      # Remove default attrs so that Modules created by a tensorflow version
      # with ops that have new attrs that are left to their default values can
      # still be loaded by older versions unware of those attributes.
      meta_graph = tf_v1.train.export_meta_graph(strip_default_attrs=True)
      _export_tags(meta_graph, tags)
      _export_signatures(meta_graph)
      _export_module_attachments(meta_graph)
    self._proto.meta_graphs.extend([meta_graph])