code: function checkFunction(node) {
              const parent = node.parent;
  
              if (parent.type === "CallExpression") {
                  callbackStack.push(node);
              }
  
              if (callbackStack.length > THRESHOLD) {
                  const opts = { num: callbackStack.length, max: THRESHOLD };
  
                  context.report({ node, messageId: "exceed", data: opts });
              }
          }
docs: Checks a given function node for too many callbacks.
  @param {ASTNode} node The node to check.
  @returns {void}
  @private