'The state the reply is currently in. A normal reply object goes
sequentially through the following lifecycle:
1. start: Initial State.
2. taken: The reply object has been taken to be commited.
3. committed: The reply has been sent back to the requesting party.
This attribute is read-only and can only be modified by calling one of
state transition functions.'

@property
def state(self):

    return self._state
