def METHOD_NAME():
    graph = graph_0()
    assert set(graph.children_of('a')) == {'d', 'e'}
    assert set(graph.children_of('b')) == {'d', 'e'}
    assert set(graph.children_of('c')) == {'f'}
    assert set(graph.children_of('d')) == {'f'}
    assert set(graph.children_of('e')) == {'g'}
    assert set(graph.children_of('f')) == set()
    assert set(graph.children_of('g')) == set()