fix convert_to_tf

pytorch_transformers/convert_pytorch_checkpoint_to_tf.py

@@ -72,11 +72,11 @@ def convert_pytorch_checkpoint_to_tf(model:BertModel, ckpt_dir:str, model_name:s
         return 'bert/{}'.format(name)
 
     def assign_tf_var(tensor:np.ndarray, name:str):
-        tmp_var = tf.Variable(initial_value=tensor)
-        tf_var = tf.get_variable(dtype=tmp_var.dtype, shape=tmp_var.shape, name=name)
-        op = tf.assign(ref=tf_var, value=tmp_var)
-        session.run(tf.variables_initializer([tmp_var, tf_var]))
-        session.run(fetches=[op, tf_var])
+        tf_dtype = tf.dtypes.as_dtype(tensor.dtype)
+        tf_var = tf.get_variable(dtype=tf_dtype, shape=tensor.shape, name=name)
+        session.run(tf.variables_initializer([tf_var]))
+        tf.keras.backend.set_value(tf_var, tensor)
+        session.run(tf_var)
         return tf_var
 
     for var_name in state_dict: