code: def __init__(self, num_class):
      self.num_class = num_class
      self.confusion_matrix = np.zeros((self.num_class,) * 2)
      self.ignore_index = None
      self.synthia = True if num_class == 16 else False
  
imports: import os
  import time
  import tqdm
  import numpy
  from PIL import Image
  import paddle
  import paddle.nn.functional
  from paddleseg.utils import metrics, TimeAverager, calculate_eta, logger, progbar
  import datasets
  from utils import save_imgs
label_desc: Use image node_id 1 to create a new Eval object  with example: obj = Eval(num_class)