code: function NullInPathError() {
      var instance = new Error("`null` and `undefined` are not allowed in branch key positions");
  
      instance.name = "NullInPathError";
  
      if (Object.setPrototypeOf) {
          Object.setPrototypeOf(instance, Object.getPrototypeOf(this));
      }
  
      if (Error.captureStackTrace) {
          Error.captureStackTrace(instance, NullInPathError);
      }
  
      return instance;
  }
docs: Does not allow null in path
  
  @private