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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 fetch_challenge(http_header):
 """ apparently keywords Basic and Digest are not being checked anywhere and decisions are being made based on authorization configuration of client, so I guess you better know what you are doing. Here I am requiring one or the other be specified. challenge Basic auth_param challenge Digest auth_param """

  m = fetch_challenge.wwwauth_header_re.match(http_header)
  if m is None:
      raise RuntimeError, 'expecting "WWW-Authenticate header [Basic,Digest]"'

  d = dict(challenge=m.groups()[0])
  m = fetch_challenge.auth_param_re.search(http_header)
  while m is not None:
      k,v = http_header[m.start():m.end()].split('=')
      d[k.lower()] = v[1:-1]
      m = fetch_challenge.auth_param_re.search(http_header, m.end())
       
  return d