manim中TextMobject is not defined的问题

最近从3blue1brown的视频知道了一个好东西：manim。可在照着示例写代码，想添加一些文字和公式时，却遇到一个报错：

NameError: name 'TextMObject' is not defined

原来是版本不一样，TextMObject改成了TexText, TexMObject改成了Tex。

可以运行的源代码如下：

from manimlib import *

class WriteStuff(Scene):
    def construct(self):
        example_text = TexText(
            "This is a some text",
            tex_to_color_map={"text": YELLOW}
        )
        example_tex = Tex(
            "\sum_{k=1}^\infty {1 \over k^2} = {\pi^2 \over 6}",
        )
        group = VGroup(example_text, example_tex)
        group.arrange(DOWN)
        group.set_width(frame_WIDTH - 2 * LARGE_BUFF)

        self.play(Write(example_text))
        self.play(Write(example_tex))
        self.wait()

参考：

python - TextMobject is not defined in Manim - Stack Overflow