code: function Morph(parent, start, end, domHelper, contextualElement) {
        if (parent.nodeType === 11) {
          ensureStartEnd(start, end);
          this.element = null;
        } else {
          this.element = parent;
        }
        this._parent = parent;
        this.start = start;
        this.end = end;
        this.domHelper = domHelper;
        ensureContext(contextualElement);
        this.contextualElement = contextualElement;
        this.reset();
      }
docs: TODO: this is an internal API, this should be an assert