code: function() {
              let results = query('select * from questionnaire');
  
              for(let questionnaire of results) {
                  // load data fields
                  questionnaire.language_data = {};
                  let dataResults = query('select field, question_td_id from questionnaire_data_field where questionnaire_id=?',
                      [questionnaire.id]);
                  for(let data of dataResults) {
                      questionnaire.language_data[data.field] = data.question_td_id;
                  }
              }
              return results;
          }
docs: Returns a list of questionnaires.
  
  @returns {[{}]} a list of questionnaires