def _rotate_point(pt: np.ndarray, angle_rad: float) -> np.ndarray:
    """Rotate a point by an angle.

    Args:
        pt (np.ndarray): 2D point coordinates (x, y) in shape (2, )
        angle_rad (float): rotation angle in radian

    Returns:
        np.ndarray: Rotated point in shape (2, )
    """

    sn, cs = np.sin(angle_rad), np.cos(angle_rad)
    rot_mat = np.array([[cs, -sn], [sn, cs]])
    return rot_mat @ pt
Rotate a point by an angle.

    Args:
        pt (np.ndarray): 2D point coordinates (x, y) in shape (2, )
        angle_rad (float): rotation angle in radian

    Returns:
        np.ndarray: Rotated point in shape (2, )
    
mmpose/mmpose/structures/bbox/transforms.py