tranform graph elems

from functools import reduce

g = {1:{2,3,4}, 2:{1,3}, 3:{1,4}, 4:{1,3}}

def transf(graph, f):
    def reducer(acc, elem):
        aux = set(map(f, elem))
        elem.clear()
        elem.update(aux)

    reduce(reducer, graph.values(), None)
    return graph

print(transf(g, lambda x: x ** 2))