code: def flip(img, y_flip=False, x_flip=False, copy=False):
      """Flip an image in vertical or horizontal direction as specified.
  
      Args:
          img (~numpy.ndarray): An array that gets flipped. This is in CHW
              format.
          y_flip (bool): Flip in vertical direction.
          x_flip (bool): Flip in horizontal direction.
          copy (bool): If False, a view of :obj:`img` will be returned.
  
      Returns:
          Transformed :obj:`img` in CHW format.
      """
  
      assert img.ndim == 3, "The dimension of image must be 3"
      if y_flip:
          img = img[:, ::-1, :]
      if x_flip:
          img = img[:, :, ::-1]
  
      if copy:
          img = img.copy()
      return img
  
label_desc: Use image node_id 1 for calling a global function with example usage: flip(img, y_flip, x_flip, copy) and returns: img