def METHOD_NAME(self, name, functionality):
    if (name == "xy_stage"):
        self.xy_stage_fn = functionality
    elif (name == "z_stage"):
        self.z_stage_fn = functionality
        self.z_stage_center = self.z_stage_fn.getCenterPosition()
        self.z_stage_max = self.z_stage_fn.getMaximum()
        self.z_stage_min = self.z_stage_fn.getMinimum()
    else:
        print(">> Warning unknown function", name)