Use cfg_gamma instead of use_cfg boolean flag

- Makes it possible to set gamma parameter
- Setting it to `None` disabled functionality completely

skorch/llm/classifier.py

@@ -221,7 +221,9 @@ class _CFGuidance(LogitsProcessor):
     References
     ----------
 
-    [1]: TODO
+    [1]: Sanchez, Guillaume, et al.
+        "Stay on topic with Classifier-Free Guidance."
+        arXiv preprint arXiv:2306.17806 (2023).
 
     """
 
@@ -265,14 +267,14 @@ class _CacheModelWrapper:
     Set use_caching=False to disable it, e.g. for debugging.
 
     """
-    def __init__(self, model, tokenizer, use_caching=True, use_cfg=False):
+    def __init__(self, model, tokenizer, use_caching=True, cfg_gamma=None):
         self.model = model
         self.tokenizer = tokenizer
         self.use_caching = use_caching
         self.cache = {}
         self._total_calls = 0
         self._uncached_calls = 0
-        self.use_cfg = use_cfg
+        self.cfg_gamma = cfg_gamma
 
     def clear(self):
         self.cache.clear()
@@ -333,17 +335,19 @@ def generate_logits(self, *, label_id, **kwargs):
             return recorded_logits
 
         self._uncached_calls += 1  # mainly for debugging
-        guidance = _CFGuidance(
-            model=self.model,
-            label_ids=label_id,
-            tokenizer=self.tokenizer,
-        )
+
         recorder = _LogitsRecorder(
             label_ids=label_id,
             tokenizer=self.tokenizer,
         )
         processors = [recorder]
-        if self.use_cfg:
+
+        if self.cfg_gamma is not None:
+            guidance = _CFGuidance(
+                model=self.model,
+                label_ids=label_id,
+                tokenizer=self.tokenizer,
+            )
             processors.insert(0, guidance)
 
         self.model.generate(
@@ -465,7 +469,7 @@ def _fit(self, X, y, **fit_params):
         classes = [str(c) for c in self.classes_]
         self.label_ids_ = self.tokenizer_(classes)['input_ids']
         self.cached_model_ = _CacheModelWrapper(
-            self.model_, self.tokenizer_, use_caching=self.use_caching, use_cfg=self.use_cfg,
+            self.model_, self.tokenizer_, use_caching=self.use_caching, cfg_gamma=self.cfg_gamma,
         )
         return self
 
@@ -799,7 +803,7 @@ def __init__(
             error_low_prob='ignore',
             threshold_low_prob=0.0,
             use_caching=True,
-            use_cfg=False,
+            cfg_gamma=None,
     ):
         self.model_name = model_name
         self.model = model
@@ -810,7 +814,7 @@ def __init__(
         self.error_low_prob = error_low_prob
         self.threshold_low_prob = threshold_low_prob
         self.use_caching = use_caching
-        self.use_cfg = use_cfg
+        self.cfg_gamma = cfg_gamma
 
     def check_prompt(self, prompt):
         """Check if the prompt is well formed.
@@ -1030,7 +1034,7 @@ def __init__(
             error_low_prob='ignore',
             threshold_low_prob=0.0,
             use_caching=True,
-            use_cfg=False,
+            cfg_gamma=None,
             random_state=None,
     ):
         self.model_name = model_name
@@ -1043,7 +1047,7 @@ def __init__(
         self.error_low_prob = error_low_prob
         self.threshold_low_prob = threshold_low_prob
         self.use_caching = use_caching
-        self.use_cfg = use_cfg
+        self.cfg_gamma = cfg_gamma
         self.random_state = random_state
 
     def check_prompt(self, prompt):