old_contents: def flip_keypoint(keypoint, size, x_flip=False, y_flip=False):
      """Modify keypoints according to image flips.
  
      Args:
          keypoint (~numpy.ndarray): Keypoints in the image.
              The shape of this array is :math:`(K, 2)`. :math:`K` is the number
              of keypoint in the image.
              The last dimension is composed of :math:`x` and :math:`y`
              coordinates of the keypoints.
          size (tuple): A tuple of length 2. The width and the height
              of the image before resized.
          x_flip (bool): Modify keypoints according to a horizontal flip of
              an image.
          y_flip (bool): Modify keypoints according to a vertical flip of
              an image.
  
      Returns:
          ~numpy.ndarray:
          Keypoint modified according to image flips.
  
      """
      W, H = size
      keypoint = keypoint.copy()
      if x_flip:
          keypoint[:, 0] = W - 1 - keypoint[:, 0]
      if y_flip:
          keypoint[:, 1] = H - 1 - keypoint[:, 1]
      return keypoint
  
new_contents: def flip_keypoint(keypoint, size, x_flip=False, y_flip=False):
      """Modify keypoints according to image flips.
  
      Args:
          keypoint (~numpy.ndarray): Keypoints in the image.
              The shape of this array is :math:`(K, 2)`. :math:`K` is the number
              of keypoints in the image.
              The last dimension is composed of :math:`x` and :math:`y`
              coordinates of the keypoints.
          size (tuple): A tuple of length 2. The width and the height
              of the image before resized.
          x_flip (bool): Modify keypoints according to a horizontal flip of
              an image.
          y_flip (bool): Modify keypoints according to a vertical flip of
              an image.
  
      Returns:
          ~numpy.ndarray:
          Keypoints modified according to image flips.
  
      """
      W, H = size
      keypoint = keypoint.copy()
      if x_flip:
          keypoint[:, 0] = W - 1 - keypoint[:, 0]
      if y_flip:
          keypoint[:, 1] = H - 1 - keypoint[:, 1]
      return keypoint
  
subject: fix doc