Return true if this latch has already been released (i.e., the number of events the latch is waiting on is 0), and false otherwise. This method does not block. Note that a return value of true indicates a permanent state change (the latch has released and will never be un‐released), but a return value of false is ephemeral and cannot typically be acted upon without additional external state information. Also note that a return value of true does not guarantee this object is safe to destroy.