py3 compatibility

research/object_detection/model_lib.py

@@ -436,7 +436,7 @@ def create_model_fn(detection_model_fn, configs, hparams, use_tpu=False):
 
       # Eval metrics on a single example.
       eval_metric_ops = eval_util.get_eval_metric_ops_for_evaluators(
-          eval_config, category_index.values(), eval_dict)
+          eval_config, list(category_index.values()), eval_dict)
       for loss_key, loss_tensor in iter(losses_dict.items()):
         eval_metric_ops[loss_key] = tf.metrics.mean(loss_tensor)
       for var in optimizer_summary_vars: