code: @Override
      public SipHeader ensure() {
          final Function<SipHeader, ? extends SipHeader> framer = SipParser.getFramer(this.name);
          if (framer != null) {
              return framer.apply(this);
          }
          return this;
      }
docs: If this method actually gets called it means that we are the {@link SipHeaderImpl} itself
  and that we need to frame it further. Subclasses MUST override this method and simply return
  'this'.