class_docstr: A preprocessor for tf.data.Dataset.
  
  A preprocessor transforms the dataset using `tf.data` operations.
code: def get_config(self):
      return {}
  
file_path: autokeras/autokeras/engine/preprocessor.py
imports: from autokeras.engine import serializable
label_desc: Use image node_id 3 for calling the Preprocessor obj's underlying member method code with example usage: obj.get_config() and returns: dict