code: function getUpperFunction(node) {
      for (let currentNode = node; currentNode; currentNode = currentNode.parent) {
          if (anyFunctionPattern.test(currentNode.type)) {
              return currentNode;
          }
      }
      return null;
  }
docs: Finds a function node from ancestors of a node.
  @param {ASTNode} node - A start node to find.
  @returns {Node|null} A found function node.