public function modelSingular(RelationInterface $relation)
    {
        if (!isset($this->_modelSingular[$relation->getPropertyName()])) {
            $parts = explode('\\', $relation->getRelatedEntity());
            $this->_modelSingular[$relation->getPropertyName()] = lcfirst(end($parts));
        }
        return $this->_modelSingular[$relation->getPropertyName()];
    }