Merge branch 'tf_converter' into 'master'

fix 'op not unique' error in converting model from tf

See merge request deep-computing/mace!1242

tools/python/transform/tensorflow_converter.py

@@ -142,6 +142,7 @@ TFTransformGraphOptions = [
     'fold_old_batch_norms',
     'remove_control_dependencies',
     'strip_unused_nodes',
+    'merge_duplicate_nodes',
     'sort_by_execution_order'
 ]