def invalidate(self):
for key in [k for k in type(self).properties.keys()<EOL>if not type(self).properties[k].identifier]:<EOL><INDENT>self._set(key, None)<EOL><DEDENT>self._set('<STR_LIT>', False)<EOL>
Invalidates all non-identifier Properties this object has locally,
causing the next access to re-fetch them from the server