code: def model_fit(model, df_clean):
      model_fit = TfidfRecommender(
          id_col="cord_uid", tokenization_method="scibert"
      )
      tf, vectors_tokenized = model_fit.tokenize_text(df_clean)
      model_fit.fit(tf, vectors_tokenized)
  
      return model_fit
  
file_path: recommenders/tests/unit/recommenders/models/test_tfidf_utils.py
imports: import pytest
  import scipy
  import pandas
  from recommenders.models.tfidf.tfidf_utils import TfidfRecommender
label_desc: Use image node_id 4 for calling a global function with example usage: model_fit(model, df_clean) and returns: model_fit