code: public function format($format = null)
      {
          if (null === $format) {
              $format = $this->_format;
          }
  
          return parent::format($format);
      }
docs: Returns date formatted according to given format.
  
  If `$format` is `null`, it'll use `Benri_Util_DateTime::$_format`.
  
  @param string $format Format accepted by
  [date()](https://php.net/manual/en/function.date.php#refsect1-function.date-parameters)
  @return string
  @see Benri_Util_DateTime::setFormat() Benri_Util_DateTime::setFormat()