var instance = new GC.Spread.CalcEngine.Functions.Function(name,
                                                          minArgs,
                                                          maxArgs,
                                                          functionDescription,
                                                          functionDescription.description,
                                                          functionDescription.parameter,
                                                          functionDescription.parameter.name,
                                                          functionDescription.parameter.repeatable,
                                                          functionDescription.parameter.optional);
var value; // Type: boolean
value = instance.isBranch();