Fixed the docstring and type hint for forced_decoder_ids option in Ge… (#19640)

src/transformers/generation_logits_process.py

@@ -735,10 +735,11 @@ class SuppressTokensLogitsProcessor(LogitsProcessor):
 
 
 class ForceTokensLogitsProcessor(LogitsProcessor):
-    r"""This processor can be used to force a list of tokens. The processor will set their log probs to `inf` so that they
-    are sampled at their corresponding index."""
+    r"""This processor takes a list of pairs of integers which indicates a mapping from generation indices to token
+    indices that will be forced before sampling. The processor will set their log probs to `inf` so that they are
+    sampled at their corresponding index."""
 
-    def __init__(self, force_token_map):
+    def __init__(self, force_token_map: List[List[int]]):
         self.force_token_map = dict(force_token_map)
 
     def __call__(self, input_ids, scores):

src/transformers/generation_tf_logits_process.py

@@ -547,10 +547,11 @@ class TFSuppressTokensLogitsProcessor(TFLogitsProcessor):
 
 
 class TFForceTokensLogitsProcessor(TFLogitsProcessor):
-    r"""This processor can be used to force a list of tokens. The processor will set their log probs to `0` and all
-    other tokens to `-inf` so that they are sampled at their corresponding index."""
+    r"""This processor takes a list of pairs of integers which indicates a mapping from generation indices to token
+    indices that will be forced before sampling. The processor will set their log probs to `0` and all other tokens to
+    `-inf` so that they are sampled at their corresponding index."""
 
-    def __init__(self, force_token_map):
+    def __init__(self, force_token_map: List[List[int]]):
         force_token_map = dict(force_token_map)
         # Converts the dictionary of format {index: token} containing the tokens to be forced to an array, where the
         # index of the array corresponds to the index of the token to be forced, for XLA compatibility.

src/transformers/generation_tf_utils.py

@@ -406,7 +406,7 @@ class TFGenerationMixin:
         forced_eos_token_id=None,
         suppress_tokens: Optional[List[int]] = None,
         begin_suppress_tokens: Optional[List[int]] = None,
-        forced_decoder_ids: Optional[List[int]] = None,
+        forced_decoder_ids: Optional[List[List[int]]] = None,
         **model_kwargs,
     ) -> Union[TFGreedySearchOutput, TFSampleOutput, TFBeamSearchOutput, TFBeamSampleOutput, tf.Tensor]:
         r"""
@@ -506,8 +506,10 @@ class TFGenerationMixin:
             begin_suppress_tokens  (`List[int]`, *optional*, defaults to `model.config.begin_suppress_tokens`):
                 A list of tokens that will be supressed at the begining of the generation. The `SupressBeginTokens`
                 logit processor will set their log probs to `-inf` so that they are not sampled.
-            forced_decoder_ids (`List[int]`, *optional*, defaults to `model.config.forced_decoder_ids`):
-                A list of tokens that will be forced as beginning tokens, before sampling.
+            forced_decoder_ids (`List[List[int]]`, *optional*, defaults to `model.config.forced_decoder_ids`):
+                A list of pairs of integers which indicates a mapping from generation indices to token indices that
+                will be forced before sampling. For example, `[[1, 123]]` means the second generated token will always
+                be a token of index 123.
             model_specific_kwargs:
                 Additional model specific kwargs will be forwarded to the `forward` function of the model.
 
@@ -1493,9 +1495,10 @@ class TFGenerationMixin:
             begin_suppress_tokens  (`List[int]`, *optional*, defaults to `model.config.begin_suppress_tokens`):
                 A list of tokens that will be supressed at the begining of the generation. The `SupressBeginTokens`
                 logit processor will set their log probs to `-inf` so that they are not sampled.
-            forced_decoder_ids (`List[int]`, *optional*, defaults to `model.config.forced_decoder_ids`):
-                A list of tokens that will be forced as beginning tokens.
-
+            forced_decoder_ids (`List[List[int]]`, *optional*, defaults to `model.config.forced_decoder_ids`):
+                A list of pairs of integers which indicates a mapping from generation indices to token indices that
+                will be forced before sampling. For example, `[[1, 123]]` means the second generated token will always
+                be a token of index 123.
             model_kwargs:
                 Additional model specific kwargs will be forwarded to the `call` function of the model.
 
@@ -2147,7 +2150,7 @@ class TFGenerationMixin:
         forced_eos_token_id: int,
         suppress_tokens: Optional[List[int]] = None,
         begin_suppress_tokens: Optional[List[int]] = None,
-        forced_decoder_ids: Optional[List[int]] = None,
+        forced_decoder_ids: Optional[List[List[int]]] = None,
     ) -> TFLogitsProcessorList:
         """
         This class returns a [`TFLogitsProcessorList`] list object that contains all relevant [`TFLogitsProcessor`]

src/transformers/generation_utils.py

@@ -696,7 +696,7 @@ class GenerationMixin:
         renormalize_logits: Optional[bool],
         suppress_tokens: Optional[List[int]] = None,
         begin_suppress_tokens: Optional[List[int]] = None,
-        forced_decoder_ids: Optional[List[int]] = None,
+        forced_decoder_ids: Optional[List[List[int]]] = None,
     ) -> LogitsProcessorList:
         """
         This class returns a [`LogitsProcessorList`] list object that contains all relevant [`LogitsProcessor`]
@@ -956,7 +956,7 @@ class GenerationMixin:
         exponential_decay_length_penalty: Optional[Tuple[int, float]] = None,
         suppress_tokens: Optional[List[int]] = None,
         begin_suppress_tokens: Optional[List[int]] = None,
-        forced_decoder_ids: Optional[List[int]] = None,
+        forced_decoder_ids: Optional[List[List[int]]] = None,
         **model_kwargs,
     ) -> Union[GreedySearchOutput, SampleOutput, BeamSearchOutput, BeamSampleOutput, torch.LongTensor]:
         r"""
@@ -1121,9 +1121,10 @@ class GenerationMixin:
             begin_suppress_tokens  (`List[int]`, *optional*, defaults to `model.config.begin_suppress_tokens`):
                 A list of tokens that will be supressed at the begining of the generation. The `SupressBeginTokens`
                 logit processor will set their log probs to `-inf` so that they are not sampled.
-            forced_decoder_ids (`List[int]`, *optional*, defaults to `model.config.forced_decoder_ids`):
-                A list of tokens that will be forced as beginning tokens, before sampling.
-
+            forced_decoder_ids (`List[List[int]]`, *optional*, defaults to `model.config.forced_decoder_ids`):
+                A list of pairs of integers which indicates a mapping from generation indices to token indices that
+                will be forced before sampling. For example, `[[1, 123]]` means the second generated token will always
+                be a token of index 123.
             model_kwargs:
                 Additional model specific kwargs will be forwarded to the `forward` function of the model. If the model
                 is an encoder-decoder model, encoder specific kwargs should not be prefixed and decoder specific kwargs