code: def read_trailer_lines(self):
          
          if not self.closed:
              raise ValueError(
                  'Cannot read trailers until the request body has been read.',
              )
  
          while True:
              line = self.rfile.readline()
              if not line:
                  # No more data--illegal end of headers
                  raise ValueError('Illegal end of headers.')
  
              self.bytes_read += len(line)
              if self.maxlen and self.bytes_read > self.maxlen:
                  raise IOError('Request Entity Too Large')
  
              if line == CRLF:
                  # Normal end of headers
                  break
              if not line.endswith(CRLF):
                  raise ValueError('HTTP requires CRLF terminators')
  
              yield line
docs: Read HTTP headers and yield them.
  
          Returns:
              Generator: yields CRLF separated lines.