code: public function generate()
      {
          $return = sprintf(
              '<fieldset id="ctrl_%s" class="checkbox_container">
  ',
              $this->strName
          );
  
          $count = 0;
  
          if ($this->options && is_array($this->options)) {
              if ($this->arrConfiguration['includeBlankOption']) {
                  $return .= $this->generateOption(
                      array('value' => '--none--', 'label' => $this->arrConfiguration['blankOptionLabel']),
                      $count++
                  );
              }
  
              // Select all tags.
              $return .= $this->generateOption(
                  array('value' => '--all--', 'label' => $GLOBALS['TL_LANG']['metamodels_frontendfilter']['select_all']),
                  $count++
              );
  
              foreach ($this->options as $val) {
                  $return .= $this->generateOption($val, $count++);
              }
          } else {
              // Do not filter.
              if ($this->arrConfiguration['includeBlankOption']) {
                  $return .= $this->generateOption(
                      array
                      (
                          'value' => '',
                          'label' => $this->arrConfiguration['blankOptionLabel'] .
                              '<span>' .
                              $GLOBALS['TL_LANG']['metamodels_frontendfilter']['no_combinations'] .
                              '</span>'
                      ),
                      $count
                  );
              }
          }
  
          $return .= '</fieldset>';
  
          return $return;
      }
docs: {@inheritDoc}
  
  @SuppressWarnings(PHPMD.Superglobals)
  @SuppressWarnings(PHPMD.CamelCaseVariableName)