fix mt5 config (#8832)

Author: patrickvonplaten

src/transformers/models/mt5/configuration_mt5.py

@@ -60,6 +60,8 @@ class MT5Config(PretrainedConfig):
             testing).
         feed_forward_proj (:obj:`string`, `optional`, defaults to :obj:`"gated-gelu"`):
             Type of feed forward layer to be used. Should be one of :obj:`"relu"` or :obj:`"gated-gelu"`.
+        use_cache (:obj:`bool`, `optional`, defaults to :obj:`True`):
+            Whether or not the model should return the last key/values attentions (not used by all models).
     """
     model_type = "mt5"
     keys_to_ignore_at_inference = ["past_key_values"]
@@ -79,6 +81,7 @@ def __init__(
         initializer_factor=1.0,
         feed_forward_proj="gated-gelu",
         is_encoder_decoder=True,
+        use_cache=True,
         tokenizer_class="T5Tokenizer",
         tie_word_embeddings=False,
         pad_token_id=0,
@@ -109,6 +112,7 @@ def __init__(
         self.layer_norm_epsilon = layer_norm_epsilon
         self.initializer_factor = initializer_factor
         self.feed_forward_proj = feed_forward_proj
+        self.use_cache = use_cache
 
     @property
     def hidden_size(self):