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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_downstream_causal_subgraph(graph, nbunch: Union[BaseEntity, Iterable[BaseEntity]]):
 """Induce a sub-graph from all of the downstream causal entities of the nodes in the nbunch. :type graph: pybel.BELGraph :rtype: pybel.BELGraph """

    return get_subgraph_by_edge_filter(graph, build_downstream_edge_predicate(nbunch))