def keypoint_hflip(kp, rows, cols):
x, y, angle, scale = kp<EOL>c = math.cos(angle)<EOL>s = math.sin(angle)<EOL>angle = math.atan2(s, -c)<EOL>return [(cols - <NUM_LIT:1>) - x, y, angle, scale]<EOL>
Flip a keypoint horizontally around the y-axis.