code: function removeChild(node) {
      if (tree.Logical.getParentNode(node) !== this) {
        throw Error('The node to be removed is not a child of this node: ' +
          node);
      }
      if (!mixinImpl.removeNode(node)) {
        // if removing from a shadyRoot, remove form host instead
        var container = isShadyRoot(this) ?
          this.host :
          this;
        // not guaranteed to physically be in container; e.g.
        // undistributed nodes.
        var parent = tree.Composed.getParentNode(node);
        if (container === parent) {
          tree.Composed.removeChild(container, node);
        }
      }
      mixinImpl._scheduleObserver(this, null, node);
      return node;
    }
docs: Removes the given `node` from the element's `lightChildren`.
  This method also performs dom composition.