Get registry storage

		:return: WTaskRegistryBase

def registry_storage(cls):
		""" Get registry storage

		:return: WTaskRegistryBase
		"""
		if cls.__registry_storage__ is None:
			raise ValueError('__registry_storage__ must be defined')
		if isinstance(cls.__registry_storage__, WTaskRegistryBase) is False:
			raise TypeError("Property '__registry_storage__' is invalid (must derived from WTaskRegistryBase)")

		return cls.__registry_storage__