fix tokenizer to tensors

pytorch_transformers/tokenization_utils.py

@@ -27,6 +27,8 @@ from .file_utils import cached_path, is_tf_available, is_torch_available
 
 if is_tf_available():
     import tensorflow as tf
+if is_torch_available()
+    import torch
 
 logger = logging.getLogger(__name__)
 
@@ -849,7 +851,11 @@ class PreTrainedTokenizer(object):
         if return_tensors == 'tf' and is_tf_available():
             sequence = tf.constant(sequence)
             token_type_ids = tf.constant(token_type_ids)
-        elif return_tensors = 'pt' and is
+        elif return_tensors == 'pt' and is_torch_available():
+            sequence = torch.tensor(sequence)
+            token_type_ids = torch.tensor(token_type_ids)
+        elif return_tensors is not None:
+            logger.warning("Unable to convert output to tensors format {}, PyTorch or TensorFlow is not available.".format(return_tensors))
 
         encoded_inputs["input_ids"] = sequence
         encoded_inputs["token_type_ids"] = token_type_ids