def keypoint_vflip(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 [x, (rows - <NUM_LIT:1>) - y, angle, scale]<EOL>
Flip a keypoint vertically around the x-axis.