Returns the matching MetaGraphDef or raises KeyError.

def get_meta_graph(self, tags=None):
    """Returns the matching MetaGraphDef or raises KeyError."""
    matches = [meta_graph
               for meta_graph in self.meta_graphs
               if set(meta_graph.meta_info_def.tags) == set(tags or [])]
    if not matches:
      raise KeyError("SavedModelHandler has no graph with tags: %r" % tags)
    if len(matches) != 1:
      raise KeyError(
          "SavedModelHandler has multiple graphs with tags %r" % tags)
    return matches[0]