code: def contrast(
      im: np.ndarray, contrast_lower: float, contrast_upper: float
  ) -> np.ndarray:
      """
      Randomly disturb the contrast of the picture, user can use np.random.seed to fix the random behavior.
  
      Args:
          im(np.ndarray): Input image.
          contrast_lower(float): Lower bound of contrast.
          contrast_upper(float): Upper bound of contrast.
      """
      contrast_delta = np.random.uniform(contrast_lower, contrast_upper)
      im = PIL.ImageEnhance.Contrast(im).enhance(contrast_delta)
      return im
  
file_path: PaddleHub/paddlehub/vision/functional.py
imports: import os
  from typing import List, Union
  import cv2
  import PIL
  import numpy
label_desc: Use image node_id 8 for calling a global function with example usage: contrast(im, contrast_lower, contrast_upper) and returns: im