'Change the button label when the maximal number of attributes changes.
The method does not reset anything so the user can still see the
results until actually restarting the search.'

def max_attr_changed(self):

    if ((self.max_attrs != self.last_run_max_attr) or (self.saved_state is None)):
        self.button.setText('Start')
    else:
        self.button.setText('Continue')
    self.button.setEnabled(self.check_preconditions())
