自己训练的tensorflow mobilenetv1-ssd 不能转换rknn模型

我利用的tensorflow mobilenet-ssd 和官方的ssd_mobilenet_v1_coco 一样。但是报错如下：

--> Loading model
E Catch exception when loading tensorflow model: ./frozen_inference_graph.pb!
T Traceback (most recent call last):
T   File "rknn/api/rknn_base.py", line 132, in rknn.api.rknn_base.RKNNBase.load_tensorflow
T   File "rknn/base/RKNNlib/converter/convert_tf.py", line 95, in rknn.base.RKNNlib.converter.convert_tf.convert_tf.__init__
T   File "rknn/base/RKNNlib/converter/tensorflowloader.py", line 53, in rknn.base.RKNNlib.converter.tensorflowloader.TF_Graph_Preprocess.__init__
T AttributeError: 'NoneType' object has no attribute 'op'
done
--> Building model
E Catch exception when building RKNN model!
T Traceback (most recent call last):
T   File "rknn/api/rknn_base.py", line 459, in rknn.api.rknn_base.RKNNBase.build
T   File "rknn/api/rknn_base.py", line 939, in rknn.api.rknn_base.RKNNBase._quantize
T   File "rknn/base/RKNNlib/console/utils.py", line 7, in rknn.base.RKNNlib.console.utils.get_model_data_file
T   File "/usr/lib/python3.6/posixpath.py", line 122, in splitext
T     p = os.fspath(p)
T TypeError: expected str, bytes or os.PathLike object, not NoneType
done
E RKNN model data is None, please load model first!