fix #808

pytorch_transformers/modeling_openai.py

@@ -404,6 +404,8 @@ OPENAI_GPT_START_DOCSTRING = r"""    OpenAI GPT model was proposed in
 OPENAI_GPT_INPUTS_DOCSTRING = r"""    Inputs:
         **input_ids**: ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:
             Indices of input sequence tokens in the vocabulary.
+            GPT is a model with absolute position embeddings so it's usually advised to pad the inputs on
+            the right rather than the left.
             Indices can be obtained using :class:`pytorch_transformers.BPT2Tokenizer`.
             See :func:`pytorch_transformers.PreTrainedTokenizer.encode` and
             :func:`pytorch_transformers.PreTrainedTokenizer.convert_tokens_to_ids` for details.