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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 flatten(l):
 """ Flatten an arbitrarily nested sequence. Parameters l : sequence The non string sequence to flatten Notes ----- This doesn't consider strings sequences. Returns ------- flattened : generator """

    for el in l:
        if _iterable_not_string(el):
            for s in flatten(el):
                yield s
        else:
            yield el