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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 _get_cert_expiration_time(headers):
 """Get the expiration time for a cert, given the response headers. Get expiration time from the headers in the result. If we can't get a time from the headers, this returns 0, indicating that the cert shouldn't be cached. Args: headers: A dict containing the response headers from the request to get certs. Returns: An integer with the number of seconds the cert should be cached. This value is guaranteed to be >= 0. """

  # Check the max age of the cert.
  cache_control = headers.get('Cache-Control', '')
  # http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2 indicates only
  # a comma-separated header is valid, so it should be fine to split this on
  # commas.
  for entry in cache_control.split(','):
    match = _MAX_AGE_REGEX.match(entry)
    if match:
      cache_time_seconds = int(match.group(1))
      break
  else:
    return 0

  # Subtract the cert's age.
  age = headers.get('Age')
  if age is not None:
    try:
      age = int(age)
    except ValueError:
      age = 0
    cache_time_seconds -= age

  return max(0, cache_time_seconds)