def add_portable_factory(self, factory_id, factory):
self.portable_factories[factory_id] = factory<EOL>
Helper method for adding Portable factory.
example:
    >>> portable_factory = {PortableClass_0.CLASS_ID : PortableClass_0, PortableClass_1.CLASS_ID : PortableClass_1}
    >>> serialization_config.portable_factories[FACTORY_ID] = portable_factory

:param factory_id: (int), factory-id to register.
:param factory: (Dictionary), the factory dictionary of class-id:class-constructor-function pairs.