code: def contentEncoding(requestHeaders, encoding=None):
      
      if encoding is None:
          encoding = b'utf-8'
      headers = _splitHeaders(
          requestHeaders.getRawHeaders(b'Content-Type', []))
      if headers:
          return headers[0][1].get(b'charset', encoding)
      return encoding
docs: Extract an encoding from a ``Content-Type`` header.
  
      @type  requestHeaders: `twisted.web.http_headers.Headers`
      @param requestHeaders: Request headers.
  
      @type  encoding: `bytes`
      @param encoding: Default encoding to assume if the ``Content-Type``
          header is lacking one. Defaults to ``UTF-8``.
  
      @rtype: `bytes`
      @return: Content encoding.