code: def get_multi_causal_upstream(graph, nbunch: Union[BaseEntity, Iterable[BaseEntity]]):
      
      result = get_upstream_causal_subgraph(graph, nbunch)
      expand_upstream_causal(graph, result)
      return result
docs: Get the union of all the 2-level deep causal upstream subgraphs from the nbunch.
  
      :param pybel.BELGraph graph: A BEL graph
      :param nbunch: A BEL node or list of BEL nodes
      :return: A subgraph of the original BEL graph
      :rtype: pybel.BELGraph