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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 header_decode(s):
 """Decode a string encoded with RFC 2045 MIME header `Q' encoding. This function does not parse a full MIME header value encoded with quoted-printable (like =?iso-8895-1?q?Hello_World?=) -- please use the high level email.header class for that functionality. """

    s = s.replace('_', ' ')
    return re.sub(r'=[a-fA-F0-9]{2}', _unquote_match, s, re.ASCII)