protected function getCallableParameters(callable $callable)/*# : array */
    {
        // array type
        if (is_array($callable)) {
            $reflector = new \ReflectionClass($callable[0]);
            $method = $reflector->getMethod($callable[1]);

        // object with __invoke() defined
        } elseif ($this->isInvocable($callable)) {
            $reflector = new \ReflectionClass($callable);
            $method = $reflector->getMethod('__invoke');

        // simple function
        } else {
            $method = new \ReflectionFunction($callable);
        }

        return $method->getParameters();
    }