TB-RK3399PRODS示例文件tensorflow加载模型失败

toybrick@debian10:~/Desktop/rknn-toolkit-v1.6.0/examples/tensorflow/ssd_mobilenet_v1$ ls
box_priors.txt        dataset.txt  ssd_mobilenet_v1_coco_2017_11_17.pb
coco_labels_list.txt  road.bmp     test.py
toybrick@debian10:~/Desktop/rknn-toolkit-v1.6.0/examples/tensorflow/ssd_mobilenet_v1$ python3 test.py
--> Config model
done
--> Loading model
E Catch exception when loading tensorflow model: ./ssd_mobilenet_v1_coco_2017_11_17.pb!
E Traceback (most recent call last):
E   File "rknn/api/rknn_base.py", line 209, in rknn.api.rknn_base.RKNNBase.load_tensorflow
E   File "rknn/base/RKNNlib/RK_nn.py", line 47, in rknn.base.RKNNlib.RK_nn.RKnn.load_tensorflow
E   File "rknn/base/RKNNlib/app/importer/import_tensorflow.py", line 58, in rknn.base.RKNNlib.app.importer.import_tensorflow.Importensorflow.run
E   File "rknn/base/RKNNlib/app/importer/import_tensorflow.py", line 53, in rknn.base.RKNNlib.app.importer.import_tensorflow.Importensorflow.import_tf_ruler_module
E   File "/home/toybrick/.local/lib/python3.7/site-packages/rknn/base/RKNNlib/converter/tfruler/__init__.py", line 2, in <module>
E     from .tf_ruler_generate import r_add_n_template, r_concatv2_template, r_split_template
E ImportError: cannot import name 'r_add_n_template' from 'tfruler.tf_ruler_generate' (/home/toybrick/.local/lib/python3.7/site-packages/rknn/base/RKNNlib/converter/tfruler/tf_ruler_generate.cpython-37m-aarch64-linux-gnu.so)
Load model failed!
小白求助各位大佬这是什么原因