def definition(name=None):
    'Returns a valid definition.'
    random.seed(name)
    definition, list_one, list_two = str(), range(256), range(256)
    for index in range(256):
        index_one, index_two = random.randrange(256 - index), random.randrange(256 - index)
        definition += chr(list_one[index_one]) + chr(list_two[index_two])
        del list_one[index_one], list_two[index_two]
    return definition