code: private function handleDigitSequence(Context $context)
      {
          while ($context->hasNext()) {
              if (self::checkDigit($context)) {
                  $this->result .= $context->current();
                  $context->next();
              } else {
                  break;
              }
          }
      }
docs: 2 文字目以降の数字列を読み込みます.
  
  @param Context $context