def associate_successors(graph, node=""):
    """
    Returns a dictionary with outer key 'successors' securing a value list
    of dictionaries associating the source, target and edge_attribute
    with the corresponding Vertex.name strings for each successor to the
    passed node.
    """
    return {
        "successors": [
            {
                "source": node,
                "target": succ,
                "edge_attribute": graph.succ[node][succ]["edge_attribute"],
            }
            for succ in graph.succ[node]
        ]
    }