format

# File activestorage/app/models/active_storage/blob/representable.rb, line 112
    def format
      if filename.extension.present? && MiniMime.lookup_by_extension(filename.extension)&.content_type == content_type
        filename.extension
      else
        MiniMime.lookup_by_content_type(content_type).extension
      end
    end