code: def value(self, new_value):
          
          if self.unit != units.Undefined and new_value.unit != self.unit:
              raise AttributeError("%s must be in %s" % (
                  self.__class__, self.unit))
          self._value = new_value
docs: Set the value of this measurement.
  
          Raises:
              AttributeError: if the new value isn't of the correct units.