Fix GenerationMixin inheritance for transformers >= 4.50 (#3)

- Fix GenerationMixin inheritance for transformers >= 4.50 (6b1b70b14f47b7cefcbdec037b19316b907d46a6)

rnnlm_model/modeling_rnnlm.py

@@ -101,7 +101,7 @@ class GRUKerasCompat(nn.Module):
         return output, h.unsqueeze(0)
 
 
-class RNNLMForCausalLM(PreTrainedModel):
+class RNNLMForCausalLM(PreTrainedModel, GenerationMixin):
     """
     RNN-based Causal Language Model for text generation.
     Compatible with HuggingFace TextGenerationPipeline.