code: def set_fixed_split(
      preprocessing_params: PreprocessingConfigDict,
  ) -> PreprocessingConfigDict:
      """Sets the split policy explicitly to a fixed split.
  
      This potentially overrides the split configuration that the user set or what came from schema defaults.
      """
  
      return {
          **preprocessing_params,
          "split": {
              "type": "fixed",
              "column": SPLIT,
          },
      }
  
file_path: ludwig/ludwig/data/utils.py
imports: from typing import Dict, Optional
  import numpy
  from ludwig.constants import DECODER, ENCODER, SPLIT
  from ludwig.types import FeatureConfigDict, PreprocessingConfigDict
  from ludwig.utils.dataframe_utils import is_dask_series_or_df
  from ludwig.utils.types import DataFrame
label_desc: Use image node_id 2 for calling a global function with example usage: set_fixed_split(preprocessing_params) and returns: dict