Add task to this storage. Depends on :attr:`.WTaskRegistryStorage.__multiple_tasks_per_tag__`
		tasks with the same __registry_tag__ can be treated as error.

		:param task_cls: task to add
		:return: None

def add(self, task_cls):
		""" Add task to this storage. Depends on :attr:`.WTaskRegistryStorage.__multiple_tasks_per_tag__`
		tasks with the same __registry_tag__ can be treated as error.

		:param task_cls: task to add
		:return: None
		"""

		registry_tag = task_cls.__registry_tag__
		if registry_tag not in self.__registry.keys():
			self.__registry[registry_tag] = [task_cls]
		elif self.__multiple_tasks_per_tag__ is True:
			self.__registry[registry_tag].append(task_cls)
		else:
			raise RuntimeError('Multiple tasks with same tag appended')