update! (DataMapper::Collection)

    # File lib/dm-core/collection.rb, line 766
        def update!(attributes = {})
          assert_update_clean_only(:update!)

          dirty_attributes = model.new(attributes).dirty_attributes

          if dirty_attributes.empty?
            true
          elsif dirty_attributes.any? { |property, value| !property.nullable? && value.nil? }
            false
          else
            unless _update(dirty_attributes)
              return false
            end

            if loaded?
              each do |resource|
                dirty_attributes.each { |property, value| property.set!(resource, value) }
                repository.identity_map(model)[resource.key] = resource
              end
            end

            true
          end
        end