<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def doc(self):
 """Docstring of property on target or override specified on PV-object."""

        return self._pv.doc or inspect.getdoc(
            getattr(type(self._target), self._pv.property, None)) or ''