docs: def bind_download_buttons(cls):
          """
          Bind buttons to callbacks.
          """
          def on_click(ev):
              button_el = ev.target
              form_el = button_el.parent.parent.parent
  
              # this allows to use disabled <textearea>, which is normally not
              # sent
              content = form_el.get(selector="textarea")[0].text
  
              # change filename according to output
              suffix = form_el.name
              download_path = "as_file/%s.%s" % (cls.filename, suffix)
              form_el.action = join(settings.API_PATH, download_path)
  
              input_el = form_el.get(selector="input")[0]
              input_el.value = content
  
          for el in document.get(selector="button.output_download_button"):
              el.bind("click", on_click)