make if statements cleaner for prepare_inputs_for_generation

src/transformers/modeling_ctrl.py

@@ -491,8 +491,9 @@ class CTRLLMHeadModel(CTRLPreTrainedModel):
         return self.lm_head
 
     def prepare_inputs_for_generation(self, input_ids, **kwargs):
-        # inputs_ids should only be composed of last token if past is in kwargs and defined
-        input_ids = input_ids[:, -1].unsqueeze(-1) if 'past' in kwargs and kwargs['past'] else input_ids
+        # only last token for inputs_ids if past is defined in kwargs
+        if 'past' in kwargs and kwargs['past']:
+            input_ids = input_ids[:, -1].unsqueeze(-1)
 
         inputs = {"input_ids": input_ids}
         inputs.update(kwargs)

src/transformers/modeling_gpt2.py

@@ -560,8 +560,9 @@ class GPT2LMHeadModel(GPT2PreTrainedModel):
         return self.lm_head
 
     def prepare_inputs_for_generation(self, input_ids, **kwargs):
-        # inputs_ids should only be composed of last token if past is in kwargs and defined
-        input_ids = input_ids[:, -1].unsqueeze(-1) if 'past' in kwargs and kwargs['past'] else input_ids
+        # only last token for inputs_ids if past is defined in kwargs
+        if 'past' in kwargs and kwargs['past']:
+            input_ids = input_ids[:, -1].unsqueeze(-1)
 
         inputs = {"input_ids": input_ids}
         inputs.update(kwargs)

src/transformers/modeling_utils.py

@@ -540,8 +540,8 @@ class PreTrainedModel(nn.Module):
         return {"input_ids": input_ids}
 
     def _do_output_past(self, outputs):
-        # TODO: might be better to write a self.do_output_past method for each individual class as is done for
-        # prepare_inputs_for_generation
+        # TODO: might be better to write a self.do_output_past method for each
+        # individual class as is done for prepare_inputs_for_generation
         has_output_past = hasattr(self.config, 'output_past') and self.config.output_past
         has_multiple_outputs = len(outputs) > 1
         has_mem_len = hasattr(self, 'mem_len')