<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def units(self):
 """ Returns the units of the measured value for the current mode. May return empty string """

        self._units, value = self.get_attr_string(self._units, 'units')
        return value