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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 non_interactions(graph, t=None):
 """Returns the non-existent edges in the graph at time t. Parameters graph : NetworkX graph. Graph to find non-existent edges. t : snapshot id (default=None) If None the non-existent edges are identified on the flattened graph. Returns ------- non_edges : iterator Iterator of edges that are not in the graph. """

    # if graph.is_directed():
    #    for u in graph:
    #        for v in non_neighbors(graph, u, t):
    #            yield (u, v)
    #else:
    nodes = set(graph)
    while nodes:
        u = nodes.pop()
        for v in nodes - set(graph[u]):
            yield (u, v)