docs: private boolean isPreamble(int index) {
          if (index <= buffer.length() - 6) {
              if (
                      buffer.get(index)     == '<' && 
                      buffer.get(index + 1) == '?' && 
                      buffer.get(index + 2) == 'x' && 
                      buffer.get(index + 3) == 'm' && 
                      buffer.get(index + 4) == 'l' && 
                      buffer.get(index + 5) == ' '
                  ) {
                  return true;
              }
          }
          return false;
      }