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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 _unbytes(bytestr):
 """ Returns a bytestring from the human-friendly string returned by `_bytes`. '\x12\x34\x56' """

    return ''.join(chr(int(bytestr[k:k + 2], 16))
                   for k in range(0, len(bytestr), 2))