class_docstr: normalize image
  Args:
      mean (list): im - mean
      std (list): im / std
      is_scale (bool): whether need im / 255
      is_channel_first (bool): if True: image shape is CHW, else: HWC
code: def __init__(self, mean, std, is_scale=True, is_channel_first=False):
      self.mean = mean
      self.std = std
      self.is_scale = is_scale
      self.is_channel_first = is_channel_first
  
imports: import cv2
  import numpy
  from PIL import Image
label_desc: Use image node_id 1 to create a new Normalize object from inherited base classes: object with example: obj = Normalize(mean, std, is_scale, is_channel_first)