/**
  * Find a model by its primary key.
  *
  * @param mixed $id
  * @param array $columns
  *
  * @return \Illuminate\Database\Eloquent\Model|static|null
  */
 public function find($id, $columns = array('*'))
 {
     Event::fire('before.find', array($this));
     $result = parent::find($id, $columns);
     Event::fire('after.find', array($this));
     return $result;
 }