code: def on_epoch_begin(self, epoch, logs=None):
      self.model.save_weights(
          self.ckpt_dir + "/epoch_" + str(epoch) + ".h5"
      )
  
file_path: DALI/docs/examples/use_cases/tensorflow/yolov4/src/train.py
imports: from model import YOLOv4Model
  import numpy
  import tensorflow
  from dali.pipeline import YOLOv4Pipeline
  from np.pipeline import YOLOv4PipelineNumpy
  import os
  import random
  import atexit
label_desc: Use image node_id 2 for calling the SaveWeightsCallback obj's underlying member method code with example usage: obj.on_epoch_begin(epoch, logs) without return types