docstr: Called before preprocessing for evaluation.
docstr_tok: ["Called","before","preprocessing","for","evaluation","."]
code: def on_evaluation_start(self):
      """Called before preprocessing for evaluation."""
      pass
  
imports: from abc import ABC
  from typing import Any, Callable, Dict, List, Union
  from ludwig.api_annotations import PublicAPI
  from ludwig.types import HyperoptConfigDict, ModelConfigDict, TrainingSetMetadataDict
label_desc: Use image node_id 36 for calling the Callback obj's underlying member method code with example usage: obj.on_evaluation_start() without return types