/**
  * Returns a list of all the categories belonging to a user.
  *
  * @return Collection
  */
 public function getCategories() : Collection
 {
     /** @var Collection $set */
     $set = $this->user->categories()->orderBy('name', 'ASC')->get();
     $set = $set->sortBy(function (Category $category) {
         return strtolower($category->name);
     });
     return $set;
 }