def set_font(
        self,
        font: str | None = None,
        fontsize: int = 0,
        fontshadow: ColorType = "",
    ):
        """
        Change the font used by this widget. If font is None, the current
        font is used.
        """
        if font is not None:
            self.font = font
        if fontsize != 0:
            self.fontsize = fontsize
        if fontshadow != "":
            self.fontshadow = fontshadow
        self.bar.draw()

        Change the font used by this widget. If font is None, the current
        font is used.
        
libqtile/widget/base.py