docstr: Called at the beginning of evaluation or validation.
  Subclasses should override for any actions to run.
  Args:
      logs: Dict. Currently no data is passed to this argument for this method
        but that may change in the future.
docstr_tok: ["Called","at","the","beginning","of","evaluation","or","validation",".","Subclasses","should","override","for","any","actions","to","run",".","Args",":","logs",":","Dict",".","Currently","no","data","is","passed","to","this","argument","for","this","method","but","that","may","change","in","the","future","."]
code: def on_test_begin(self, logs=None):
      """Called at the beginning of evaluation or validation.
      Subclasses should override for any actions to run.
      Args:
          logs: Dict. Currently no data is passed to this argument for this method
            but that may change in the future.
      """
      self.tf_callback.on_test_begin(logs)
  
imports: import os
  import logging
  import shutil
  import tensorflow
  from bigdl.orca.learn.utils import get_replaced_path
  from bigdl.orca.data.file import put_local_files_with_prefix_to_remote, put_local_dir_tree_to_remote, put_local_file_to_remote
label_desc: Use image node_id 16 for calling the Callback obj's underlying member method code with example usage: obj.on_test_begin(logs) without return types