@classmethod
def activate(cls, flow_task, prev_activation, token):
    """Instantiate new task."""
    task = cls.create_task(flow_task, prev_activation, token)
    task.save()
    task.previous.add(prev_activation.task)
    activation = cls()
    activation.initialize(flow_task, task)
    if activation.flow_task._on_create is not None:
        activation.flow_task._on_create(activation)
    return activation
