def images_at(cell_name)
      coordinate = calc_coordinate(cell_name)
      pathnames_at_coordinate = @images_pathnames[coordinate]
      return if pathnames_at_coordinate.empty?

      pathnames_at_coordinate.map do |image_pathname|
        if image_pathname.exist?
          image_pathname
        else
          excel_image_path = "xl/media#{image_pathname.to_path.split(tmpdir).last}"
          IO.copy_stream(@book.files.file.open(excel_image_path), image_pathname.to_path)
          image_pathname
         end
      end
    end
def images_at(cell_name)
      coordinate = calc_coordinate(cell_name)
      pathnames_at_coordinate = @images_pathnames[coordinate]
      return if pathnames_at_coordinate.empty?

      pathnames_at_coordinate.map do |image_pathname|
        if image_pathname.exist?
          image_pathname
        else
          excel_image_path = "xl/media#{image_pathname.to_path.split(tmpdir).last}"
          IO.copy_stream(@book.files.file.open(excel_image_path), image_pathname.to_path)
          image_pathname
         end
      end
    end
Extracts images from excel to tmpdir for a cell, if the images are not already extracted (multiple calls or same image file in multiple cells).
 Returns array of images as Pathname objects or nil.