def introduce_variable_area(self):
    area = self.area = self.get_area(0, 6)
    x_nums = self.x_axis.numbers
    self.play(Write(area, run_time=2))
    self.play(FadeOut(self.x_axis.numbers))
    self.add_T_label(6)
    self.change_area_bounds(new_t_max=4, rate_func=there_and_back, run_time=2)
    self.wait()
def introduce_variable_area(self):
    area = self.area = self.get_area(0, 6)
    x_nums = self.x_axis.numbers
    self.play(Write(area, run_time=2))
    self.play(FadeOut(self.x_axis.numbers))
    self.add_T_label(6)
    self.change_area_bounds(new_t_max=4, rate_func=there_and_back, run_time=2)
    self.wait()