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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 count_relations(graph) -> Counter: """Return a histogram over all relationships in a graph. :param pybel.BELGraph graph: A BEL graph :return: A Counter from {relation type: frequency} """

    return Counter(
        data[RELATION]
        for _, _, data in graph.edges(data=True)
    )