code: def process_categorical_features(df, categorical_features):
      for i in categorical_features:
          df.iloc[:, i].fillna("", inplace=True)
      return df
  
imports: import os
  from typing import Optional
  import pandas
  from ludwig.datasets.dataset_config import DatasetConfig
  from ludwig.datasets.loaders.dataset_loader import DatasetLoader
label_desc: Use image node_id 1 for calling a global function with example usage: process_categorical_features(df, categorical_features) and returns: df