code: def depth_file_for_rgb_file(rgb_filename, rgb_file_list, depth_file_list):
          
          (root, filename) = os.path.split(rgb_filename)
          rgb_timestamps = np.array(Kinect.timestamps_from_file_list(rgb_file_list))
          depth_timestamps = np.array(Kinect.timestamps_from_file_list(depth_file_list))
          needle_ts = rgb_timestamps[rgb_file_list.index(rgb_filename)]
          haystack_idx = np.argmin(np.abs(depth_timestamps - needle_ts))
          depth_filename = depth_file_list[haystack_idx]
          return depth_filename
docs: Returns the *closest* depth file from an RGB filename