code: function getChildren(node) {
      const t = node.type;
  
      if (t === "BlockStatement" || t === "Program") {
          return node.body;
      }
      if (t === "SwitchCase") {
          return node.consequent;
      }
      return null;
  }
docs: Get the child node list of a given node.
  This returns `Program#body`, `BlockStatement#body`, or `SwitchCase#consequent`.
  This is used to check whether a node is the first/last child.
  @param {Node} node A node to get child node list.
  @returns {Node[]|null} The child node list.