public function toHtml()
 {
     global $PAGE;
     $this->_generateId();
     if (!$this->_flagFrozen) {
         $PAGE->requires->string_for_js('nonematch', 'tool_editrolesbycap');
         $PAGE->requires->string_for_js('filter', 'moodle');
         $PAGE->requires->string_for_js('clear', 'moodle');
         $PAGE->requires->yui_module('moodle-tool_editrolesbycap-capabilityformfield', 'M.tool_editrolesbycap.init_capabilityformfield', array('#' . $this->getAttribute('id')));
     }
     return parent::toHtml();
 }