code: def __call__(self, x: np.ndarray) -> float:
      assert (
          x.shape == self.domain_shape
      ), f"Shape = {x.shape} vs {self.domain_shape}"
      assert x.shape[2] == 3
      x_gray_1d = np.sum(x, 2).ravel()
      ref_gray_1d = np.sum(self.reference, 2).ravel()
      value = float(np.sum(np.sort(x_gray_1d) - np.sort(ref_gray_1d)))
      return value
  
imports: import os
  import typing
  import torch
  import numpy
  import cv2
  from nevergrad.functions.base import UnsupportedExperiment
  from nevergrad.common.decorators import Registry
label_desc: Use image node_id 1 for calling the HistogramDifference obj's underlying member method code with example usage: obj.__call__(x) and returns: value