class_docstr: Auto adjust image contrast.
  
  Required Keys:
  
  - img
  
  Modified Keys:
  
  - img
  
  Args:
      prob (float): The probability for performing AutoContrast should
           be in range [0, 1]. Defaults to 1.0.
      level (int, optional): No use for AutoContrast transformation.
          Defaults to None.
      min_mag (float): No use for AutoContrast transformation.
          Defaults to 0.1.
      max_mag (float): No use for AutoContrast transformation.
          Defaults to 1.9.
docstr: Auto adjust image contrast.
docstr_tok: ["Auto","adjust","image","contrast","."]
code: def _transform_img(self, results: dict, mag: float) -> None:
      """Auto adjust image contrast."""
      img = results["img"]
      results["img"] = mmcv.auto_contrast(img).astype(img.dtype)
  
imports: import math
  from typing import Optional
  import mmcv
  import numpy
  from mmcv.transforms import BaseTransform
  from mmcv.transforms.utils import cache_randomness
  from mmdet.registry import TRANSFORMS
  from .augment_wrappers import _MAX_LEVEL, level_to_mag
label_desc: Use image node_id 1 for calling the AutoContrast obj's underlying member method code with example usage: obj._transform_img(results, mag) without return types