from typing import Sequence


def keypoint_scale(keypoint: Sequence[float], scale_x: float, scale_y: float):
    """Scales a keypoint by scale_x and scale_y.

    Args:
        keypoint (tuple): A keypoint `(x, y, angle, scale)`.
        scale_x: Scale coefficient x-axis.
        scale_y: Scale coefficient y-axis.

    Returns:
        A keypoint `(x, y, angle, scale)`.

    """
    x, y, angle, scale = keypoint[:4]
    return x * scale_x, y * scale_y, angle, scale * max(scale_x, scale_y)