anchor.diff:  
     /// Returns a Query with the ending point [value]. The ending point
     /// is inclusive.
  +  ///
  +  /// The [value] must be a [num], [String], [bool], or [null].
     /// The optional [key] can be used to further limit the range of the query.
     Query endAt(value, [String key]) => new Query.fromJsObject(
         key == null ? jsObject.endAt(value) : jsObject.endAt(value, key));
   
     /// Returns a Query which includes children which match the specified [value].
  +  ///
  +  /// The [value] must be a [num], [String], [bool], or [null].
     /// The optional [key] can be used to further limit the range of the query.
     Query equalTo(value, [String key]) => new Query.fromJsObject(
         key == null ? jsObject.equalTo(value) : jsObject.equalTo(value, key));
  
positive.code:   ///     var event = await ref.once("value");
    ///     print(event.snapshot.val()); //prints 4
    ///
    /// The returned value from [transactionUpdate] function must be
    /// a Dart [Map], [Iterable] or primitive type.
    ///
    /// Set [applyLocally] to [false] to not see intermediate states.
    Future<Transaction> transaction(Func1 transactionUpdate,
  
negative.code:   /// [newPriority].
    ///
    /// Like [set()] but also specifies the priority.
    ///
    /// The [newVal] must be a Dart basic type or the error is thrown.
    /// The [newPriority] must be a [String], [num] or [null].
    Future setWithPriority(newVal, newPriority) =>
        handleThenable(jsObject.setWithPriority(jsify(newVal), newPriority));
  
  