def all_sub_categories(params = {})
      @all_sub_categories ||= sub_categories(params) + sub_categories.flat_map do |sub|
        sub.all_sub_categories(params)
      end
    end
def all_sub_categories(params = {})
      @all_sub_categories ||= sub_categories(params) + sub_categories.flat_map do |sub|
        sub.all_sub_categories(params)
      end
    end
Public: Returns an Array of all of the sub categories (deep) for the
         Category