Fix failing torchscript tests for `CpmAnt` model (#22766)

* fix

---------
Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

src/transformers/models/cpmant/configuration_cpmant.py

@@ -69,8 +69,6 @@ class CpmAntConfig(PretrainedConfig):
             Whether to use cache.
         init_std (`float`, *optional*, defaults to 1.0):
             Initialize parameters with std = init_std.
-        return_dict (`bool`, *optional*, defaults to `True`):
-            Whether or not to return a [`~utils.ModelOutput`] instead of a plain tuple.
 
     Example:
 
@@ -105,7 +103,6 @@ class CpmAntConfig(PretrainedConfig):
         prompt_length: int = 32,
         segment_types: int = 32,
         use_cache: bool = True,
-        return_dict: bool = True,
         **kwargs,
     ):
         super().__init__(**kwargs)
@@ -123,5 +120,4 @@ class CpmAntConfig(PretrainedConfig):
         self.eps = eps
         self.use_cache = use_cache
         self.vocab_size = vocab_size
-        self.return_dict = return_dict
         self.init_std = init_std

src/transformers/models/cpmant/modeling_cpmant.py

@@ -378,7 +378,7 @@ class CpmAntEncoder(nn.Module):
         """
         all_hidden_states = () if output_hidden_states else None
         all_self_attns = () if output_attentions else None
-        current_key_values = [] if use_cache else None
+        current_key_values = () if use_cache else None
 
         for i, layer in enumerate(self.layers):
             if output_hidden_states:
@@ -395,7 +395,7 @@ class CpmAntEncoder(nn.Module):
             if output_attentions:
                 all_self_attns += (attn_weights,)
             if current_key_value is not None:
-                current_key_values.append(current_key_value)
+                current_key_values = current_key_values + (current_key_value,)
 
         hidden_states = self.output_layernorm(hidden_states)
 
@@ -659,7 +659,7 @@ class CpmAntModel(CpmAntPreTrainedModel):
         output_hidden_states = (
             output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
         )
-        return_dict = return_dict if return_dict is not None else self.config.return_dict
+        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
         use_cache = use_cache if use_cache is not None else self.config.use_cache
 
         # add prompts ahead