Method _ifNode

src/expression/node/Node.js:105–110

* Validate whether an object is a Node, for use with map * @param {Node} node * @returns {Node} Returns the input if it's a node, else throws an Error * @protected

(node)

     * @protected
     */
    _ifNode (node) {
      if (!isNode(node)) {
        throw new TypeError('Callback function must return a Node')
      }
      return node
    }

    /**
     * Recursively traverse all nodes in a node tree. Executes given callback for