implement local features using normalized patches.\ \ Normalize image intensities in a local window centered at keypoint to a\ feature vector with unit norm. This local feature is simple to code and\ works OK.\ \ Choose the top-left option of the 4 possible choices for center of a square\ window.\ \ Args:\ image_bw: array of shape (M,N) representing grayscale image\ X: array of shape (K,) representing x-coordinate of keypoints\ Y: array of shape (K,) representing y-coordinate of keypoints\ feature_width: size of the square window\ \ Returns:\ fvs: array of shape (K,D) representing feature descriptors