code: protected function value($name)
      {
          $object = isset($this->instances[$name]) ? $this->get($name) : null;
  
          $exists = ! $object && $this->extra->has($name) === true;
  
          return $exists === true ? $this->extra->get($name) : $object;
      }
docs: Returns the value of the specified argument.
  
  @param  string $name
  @return mixed|null