def save_file
      attributes[:content_type] = file.content_type if file.respond_to? :content_type
      @grid_file ? @grid_file.save : @grid_file = self.class.grid.put(file, attributes.symbolize_keys)

      persisted? ? run_callbacks(:update) : run_callbacks(:create)
    end
def save_file
      attributes[:content_type] = file.content_type if file.respond_to? :content_type
      @grid_file ? @grid_file.save : @grid_file = self.class.grid.put(file, attributes.symbolize_keys)

      persisted? ? run_callbacks(:update) : run_callbacks(:create)
    end
Make save behave like Mongoid::Document as much as possible

 @return result of #run_callbacks, @see ActiveSupport::Callbacks