code: protected void encodeHeaders(HttpHeaders headers, ByteBuf buf) {
          Iterator<Entry<CharSequence, CharSequence>> iter = headers.iteratorCharSequence();
          while (iter.hasNext()) {
              Entry<CharSequence, CharSequence> header = iter.next();
              HttpHeadersEncoder.encoderHeader(header.getKey(), header.getValue(), buf);
          }
      }
docs: Encode the {@link HttpHeaders} into a {@link ByteBuf}.