code: def get_graph_csv():
      
      assert request.method == "POST", "POST request expected received {}".format(request.method)
      if request.method == "POST":
          try:
              selected_variable_table = request.form["selected_variable_table"]
              filename = utils.generate_graph_csv(selected_variable_table)
              return send_file(filename, as_attachment=True, attachment_filename='{}.csv'.format(selected_variable_table))
          except Exception as e:
              logging.error(e)
      return jsonify({"0": "__EMPTY"})
docs: Allows the user to download a graph's data as a CSV file.
      :return: show a dialog box that allows the user to download the CSV file.