<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_parameter_scale(self, name, par, scale):
 """Update the scale of a parameter while keeping its value constant."""

        name = self.roi.get_source_by_name(name).name
        idx = self.like.par_index(name, par)
        current_bounds = list(self.like.model[idx].getBounds())
        current_scale = self.like.model[idx].getScale()
        current_value = self.like[idx].getValue()

        self.like[idx].setScale(scale)
        self.like[idx].setValue(current_value * current_scale / scale)
        self.like[idx].setBounds(current_bounds[0] * current_scale / scale,
                                 current_bounds[1] * current_scale / scale)
        self._sync_params(name)