code: def get_and_add(self, delta):
          '''
          Atomically adds `delta` to the current value and returns the old value.
  
          :param delta: The delta to add.
          '''
          with self._lock.exclusive:
              oldval = self._value
              self._value += delta
              return oldvaf get_and_add(self, delta):
          '''
          Atomically adds `delta` to the current value and returns the old value.
  
          :param delta: The delta to add.
          '''
          with self._lock.exclusive:
              oldval = self._value
              self._value += delta
              return oldval
docs: Atomically adds `delta` to the current value and returns the old value.
  
          :param delta: The delta to add.