class_docstr: Usage of that class makes sense only if you have table data.
  Stores/loads `DataPreprocessor`'s encoders and imputers for pipelines to decrease optional preprocessing time.
  
  :param cache_dir: path to the place where cache files should be stored.
docstr: Adds preprocessor into DB working table.
  
  :param pipeline: pipeline with preprocessor to add
  :param fold_id: number of fold
code: def add_preprocessor(
      self,
      pipeline: "Pipeline",
      fold_id: Optional[Union[int, None]] = None,
  ):
      """
      Adds preprocessor into DB working table.
  
      :param pipeline: pipeline with preprocessor to add
      :param fold_id: number of fold
      """
      structural_id = _get_db_uid(pipeline, fold_id)
      self._db.add_preprocessor(structural_id, pipeline.preprocessor)
  
file_path: FEDOT/fedot/core/caching/preprocessing_cache.py
imports: from typing import TYPE_CHECKING, Optional, Union
  from fedot.core.caching.base_cache import BaseCache
  from fedot.core.caching.preprocessing_cache_db import PreprocessingCacheDB
label_desc: Use image node_id 3 for calling the PreprocessingCache obj's underlying member method code with example usage: obj.add_preprocessor(pipeline, fold_id) without return types