code: public function getModel($modelName) {
          if (!isset($this->models[$modelName])) {
              throw new \LogicException(sprintf('Model for name %s doesn\'t exist!', $modelName));
          }
  
          return $this->models[$modelName];
      }
docs: @param $modelName String the name of the model.
  
  @return Model the Model corresponding to given Model name.