code: function findVariableReferences (ast, identifier, skip) {
    var references = [];
    traverse.traverse(ast, {
      enter: function (node, parent) {
        if (node === skip) {
          this.skip();
        }
        else if (
            node.type === 'Identifier' &&
            node.name === identifier.name &&
            (parent.type !== 'MemberExpression' || parent.left !== node)
        ) {
          references.push(node);
        }
      }
    });
    return references;
  }
docs: Find references to a given identifier