original_string: public static function instance($prototype = null)
      {
          if ($prototype !== null) {
              HTMLPurifier_ConfigSchema::$singleton = $prototype;
          } elseif (HTMLPurifier_ConfigSchema::$singleton === null || $prototype === true) {
              HTMLPurifier_ConfigSchema::$singleton = HTMLPurifier_ConfigSchema::makeFromSerial();
          }
          return HTMLPurifier_ConfigSchema::$singleton;
      }
code: public static function instance($prototype = null)
      {
          if ($prototype !== null) {
              HTMLPurifier_ConfigSchema::$singleton = $prototype;
          } elseif (HTMLPurifier_ConfigSchema::$singleton === null || $prototype === true) {
              HTMLPurifier_ConfigSchema::$singleton = HTMLPurifier_ConfigSchema::makeFromSerial();
          }
          return HTMLPurifier_ConfigSchema::$singleton;
      }
code_tokens: public static function instance ( $ prototype = null ) { if ( $ prototype !== null ) { HTMLPurifier_ConfigSchema :: $ singleton = $ prototype ; } elseif ( HTMLPurifier_ConfigSchema :: $ singleton === null || $ prototype === true ) { HTMLPurifier_ConfigSchema :: $ singleton = HTMLPurifier_ConfigSchema :: makeFromSerial ( ) ; } return HTMLPurifier_ConfigSchema :: $ singleton ; }
docstring: Retrieves an instance of the application-wide configuration definition.
  @param HTMLPurifier_ConfigSchema $prototype
  @return HTMLPurifier_ConfigSchema
docstring_tokens: Retrieves an instance of the application - wide configuration definition .