import copy


class Text:
    def __init__(self):
        self.lines = ""
        self.font = ""

    def write(self, lines):
        self.lines += lines

    def set_font(self, font_name):
        self.font = font_name

    def show(self):
        return "[{}]{}[{}]".format(self.font, self.lines, self.font) if self.font != "" else self.lines

    def restore(self, version):
        self.font = version.font
        self.lines = version.lines


class SavedText:
    def __init__(self):
        self.texts = []

    def save_text(self, texts):
        self.texts.append(copy.deepcopy(texts))

    def get_version(self, version):
        return self.texts[version]


if __name__ == '__main__':
    # These "asserts" using only for self-checking and not necessary for auto-testing

    text = Text()
    saver = SavedText()

    text.write("At the very beginning ")
    saver.save_text(text)
    text.set_font("Arial")
    saver.save_text(text)
    text.write("there was nothing.")

    assert text.show() == "[Arial]At the very beginning there was nothing.[Arial]"

    text.restore(saver.get_version(0))
    assert text.show() == "At the very beginning "

    print("Coding complete? Let's try tests!")