def alternative_sizes image, sizes
      data_sizes = {}
      sizes[:sizes].each do |size, value|
        if value.present?
          data_sizes["data-#{size}-src"] = (value == :default ? image.url : image.send(value))
        else
          false
        end
      end
      data_sizes
    end
def alternative_sizes image, sizes
      data_sizes = {}
      sizes[:sizes].each do |size, value|
        if value.present?
          data_sizes["data-#{size}-src"] = (value == :default ? image.url : image.send(value))
        else
          false
        end
      end
      data_sizes
    end
Loop over the images sizes and create our data attributes hash