code: def get_value(self):
          
          try:
              val = self.func()()
          except TypeError:  # The underlying function has been GC'd
              return None
  
          self.gauge_point._set(val)
          return self.gauge_point.get_value()
docs: Get the current value of the underlying measurement.
  
          Calls the tracked function and stores the value in the wrapped
          measurement as a side-effect.
  
          :rtype: int, float, or None
          :return: The current value of the wrapped function, or `None` if it no
              longer exists.