/**
  * Use this to check that a function argument is of type <code>AppInfo</code>
  *
  * @internal
  */
 public static function checkArg($argName, $argValue)
 {
     if (!$argValue instanceof self) {
         Dropbox_Checker::throwError($argName, $argValue, __CLASS__);
     }
 }
 /**
  * Check that a function argument is either <code>null</code> or of type
  * <code>WriteMode</code>.
  *
  * @internal
  */
 public static function checkArgOrNull($argName, $argValue)
 {
     if ($argValue === null) {
         return;
     }
     if (!$argValue instanceof self) {
         Dropbox_Checker::throwError($argName, $argValue, __CLASS__);
     }
 }