By default, wake up one task waiting on this condition, if any.
If the calling task has not acquired the lock when this method
is called, a RuntimeError is raised.
This method wakes up n of the tasks waiting for the condition
variable; if fewer than n are waiting, they are all awoken.
Note: an awakened task does not actually return from its
wait() call until it can reacquire the lock. Since notify() does
not release the lock, its caller should.