Rename txt model file

fast_model.py

@@ -522,7 +522,7 @@ def save_pipeline(
     pipeline_file_name : str, optional
         The filename for saving the pipeline (default is "pipeline.pkl").
     """
-    lgbm_file_name = lgbm_file_name or "model_fast_model.txt"
+    lgbm_file_name = lgbm_file_name or "model_lightgbm.txt"
     pipeline_file_name = pipeline_file_name or "pipeline.pkl"
 
     lightgbm_path = Path(path) / lgbm_file_name