class_docstr: Convert color space from RGB to LAB.
class_docstr_tok: ["Convert","color","space","from","RGB","to","LAB","."]
docstr: Convert color space from XYZ to LAB.
  
  Args:
     img(np.ndarray): Original XYZ image.
  
  Return:
      img(np.ndarray): Converted LAB image.
code: def xyz2lab(self, xyz: np.ndarray) -> np.ndarray:
      """
      Convert color space from XYZ to LAB.
  
      Args:
         img(np.ndarray): Original XYZ image.
  
      Return:
          img(np.ndarray): Converted LAB image.
      """
      sc = np.array((0.95047, 1.0, 1.08883))[:, None, None]
      xyz_scale = xyz / sc
      mask = (xyz_scale > 0.008856).astype(np.float32)
      xyz_int = np.cbrt(xyz_scale) * mask + (
          7.787 * xyz_scale + 16.0 / 116.0
      ) * (1 - mask)
      L = 116.0 * xyz_int[1, :, :] - 16.0
      a = 500.0 * (xyz_int[0, :, :] - xyz_int[1, :, :])
      b = 200.0 * (xyz_int[1, :, :] - xyz_int[2, :, :])
      out = np.concatenate(
          (L[None, :, :], a[None, :, :], b[None, :, :]), axis=0
      )
      return out
  
imports: import random
  from typing import Callable, Union, List, Tuple
  import cv2
  import PIL
  import numpy
  import paddlehub.vision.functional
label_desc: Use image node_id 2 for calling the RGB2LAB obj's underlying member method code with example usage: obj.xyz2lab(xyz) and returns: out