docs: function checkCorrectChoiceParam(that, choice) {
          if ('number' === typeof choice) choice = '' + choice;
          if ('string' !== typeof choice) {
              throw new TypeError('ChoiceTable.setCorrectChoice: each choice ' +
                                  'must be number or string. Found: ' + choice);
          }
          if ('undefined' === typeof that.choicesValues[choice]) {
  
              throw new TypeError('ChoiceTable.setCorrectChoice: choice ' +
                                  'not found: ' + choice);
          }
          return choice;
      }