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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 parse_sig(sig):
 """Parse signature integer values from s-expr."""

    label, sig = sig
    assert label == b'sig-val'
    algo_name = sig[0]
    parser = {b'rsa': _parse_rsa_sig,
              b'ecdsa': _parse_ecdsa_sig,
              b'eddsa': _parse_eddsa_sig,
              b'dsa': _parse_dsa_sig}[algo_name]
    return parser(args=sig[1:])