Inheritance: extends Illuminate\Database\Eloquent\Model
 /**
  * Add multiple categories by them names
  * to a group
  *
  * @param $group_name
  * @param $names
  * @return mixed
  */
 public function addMultipleCategoriesToGroup($group_name, array $names)
 {
     $group = $this->notificationGropup->where('name', $group_name)->first();
     $categories = $this->notificationCategory->findByNames($names);
     foreach ($categories as $category) {
         $group->categories()->attach($category->id);
     }
     return $group;
 }
 /**
  * Update a category by id.
  *
  * @param  array $data
  * @param        $categoryId
  * @return mixed
  */
 public function update(array $data, $categoryId)
 {
     return $this->categoryModel->where('id', $categoryId)->update($data);
 }