Retinanet 오류

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-17-3a306d3fab4b> in <module>
      4 # pretrained coco 모델 파일을 retinanet 모델로 로딩.
      5 from keras_retinanet import models
----> 6 retina_model = models.load_model(model_path, backbone_name='resnet50')

~\AppData\Roaming\Python\Python36\site-packages\keras_retinanet\models\__init__.py in load_model(filepath, backbone_name)
     81     """
     82     import keras.models
---> 83     return keras.models.load_model(filepath, custom_objects=backbone(backbone_name).custom_objects)
     84 
     85 

C:\anaconda3\envs\tf115\lib\site-packages\keras\engine\saving.py in load_wrapper(*args, **kwargs)
    490                 os.remove(tmp_filepath)
    491             return res
--> 492         return load_function(*args, **kwargs)
    493 
    494     return load_wrapper

C:\anaconda3\envs\tf115\lib\site-packages\keras\engine\saving.py in load_model(filepath, custom_objects, compile)
    582     if H5Dict.is_supported_type(filepath):
    583         with H5Dict(filepath, mode='r') as h5dict:
--> 584             model = _deserialize_model(h5dict, custom_objects, compile)
    585     elif hasattr(filepath, 'write') and callable(filepath.write):
    586         def load_function(h5file):

C:\anaconda3\envs\tf115\lib\site-packages\keras\engine\saving.py in _deserialize_model(h5dict, custom_objects, compile)
    271     if model_config is None:
    272         raise ValueError('No model found in config.')
--> 273     model_config = json.loads(model_config.decode('utf-8'))
    274     model = model_from_config(model_config, custom_objects=custom_objects)
    275     model_weights_group = h5dict['model_weights']

AttributeError: 'str' object has no attribute 'decode'