docs: @Override
      public byte[] generateTrailerValue(String hdr, HttpTrailers message) {
  
          HeaderKeys key = HttpHeaderKeys.find(hdr);
  
          if (key != null && hdr.equals(_key)) {
              if (tc.isDebugEnabled()) {
                  Tr.debug(tc, "generateTrailerValue(String,HttpTrailers): hdr = " + hdr + ", value = " + _value);
              }
              return _value.getBytes();
          } else if (tc.isDebugEnabled()) {
              if (tc.isDebugEnabled()) {
                  Tr.debug(tc, "generateTrailerValue(HeaderKeys,HttpTrailers): header names don't match. requested = " + hdr + ", this object = " + _key);
              }
  
          }
          return null;
      }