def f_empty(self):
raise NotImplementedError("<STR_LIT>")<EOL>
Erases all data in the parameter.

        Does not erase data from disk. So if the parameter has
        been stored with a service to disk and is emptied,
        it can be restored by loading from disk.

        :raises: ParameterLockedException: If the parameter is locked.

        ABSTRACT: Needs to be defined in subclass