Get all relations name in laravel5 model

I have model include of several relation for example like this:

public function NewsCategory()
{ 
   return $this->belongsTo("News\Model\NewsCategory");
}
public function NewsImage()
{ 
   return $this->belongsTo("News\Model\NewsImage");
}
public function NewsTag()
{ 
   return $this->belongsTo("News\Model\NewsTag");
}

and relations create dynamically.
How can I get all this class name? In this example I want
NewsCategory,NewsImage,NewsTag

via Chebli Mohamed