public function get($key, $default = null)
        {
            if ($this->has($key)) {
                $isInvokable = is_object($this->values[$this->normalizeKey($key)]) && method_exists($this->values[$this->normalizeKey($key)], '__invoke');

                return $isInvokable
                ? $this->values[$this->normalizeKey($key)]($this)
                : $this->values[$this->normalizeKey($key)];
            }

            return $default;
        }