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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 _find_unchanged(old, new):
 """ returns edges that are in both old and new """

    edges = []
    old_edges = [set(edge) for edge in old.edges()]
    new_edges = [set(edge) for edge in new.edges()]
    for old_edge in old_edges:
        if old_edge in new_edges:
            edges.append(set(old_edge))
    return edges