def METHOD_NAME(self, **features):
    @dataclass
    class MockMark(Mark):
        linewidth: float = Mappable(rc="lines.linewidth")
        pointsize: float = Mappable(4)
        color: str = Mappable("C0")
        fillcolor: str = Mappable(depend="color")
        alpha: float = Mappable(1)
        fillalpha: float = Mappable(depend="alpha")
    m = MockMark(**features)
    return m