code: def parse_headers(fp, _class=HTTPMessage):
      
      headers = []
      while True:
          line = fp.readline(_MAXLINE + 1)
          if len(line) > _MAXLINE:
              raise LineTooLong("header line")
          headers.append(line)
          if len(headers) > _MAXHEADERS:
              raise HTTPException("got more than %d headers" % _MAXHEADERS)
          if line in (b'\r\n', b'\n', b''):
              break
      hstring = bytes(b'').join(headers).decode('iso-8859-1')
      return email_parser.Parser(_class=_class).parsestr(hstring)
docs: Parses only RFC2822 headers from a file pointer.
  
      email Parser wants to see strings rather than bytes.
      But a TextIOWrapper around self.rfile would buffer too many bytes
      from the stream, bytes which we later need to read as bytes.
      So we read the correct bytes here, as bytes, for email Parser
      to parse.