def METHOD_NAME(
    request, input_shape: ShapeType
) -> Tuple[ShapeType, Optional[ShapeType]]:
    """Shapes for the first and second argument of the covariance function. The second
    shape is ``None`` if the second argument to the covariance function is ``None``."""
    x0_shape, x1_shape = request.param
    return (
        x0_shape + input_shape,
        x1_shape + input_shape if x1_shape is not None else None,
    )