docs: private boolean addInstanceOfElement(HeaderElement root, HeaderElement elem) {
          // first add to the overall sequence list
          if (null == this.hdrSequence) {
              this.hdrSequence = elem;
              this.lastHdrInSequence = elem;
          } else {
              // find the end of the list and append this new element
              this.lastHdrInSequence.nextSequence = elem;
              elem.prevSequence = this.lastHdrInSequence;
              this.lastHdrInSequence = elem;
          }
          if (null == root) {
              return true;
          }
          HeaderElement prev = root;
          while (null != prev.nextInstance) {
              prev = prev.nextInstance;
          }
          prev.nextInstance = elem;
          return false;
      }