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 });
			}
		}
Checks a given function node for too many callbacks.
@param {ASTNode} node The node to check.
@returns {void}
@private