Python tf.save_model.save投掷'；ValueError：无不支持的值'；

我正在尝试用python 3.6和tensorflow 1.14训练SSD神经网络 下面是代码，它大部分是从

每次到达最后一行时，它都会抛出以下错误：

Traceback (most recent call last):
  File "D:\Python\Threat_Assesser\retrain.py", line 78, in <module>
    tf.saved_model.save(model, saved_model_path)
  File "D:\Python\lib\site-packages\tensorflow\python\saved_model\save.py", line 822, in save
    meta_graph_def, saveable_view, signatures)
  File "D:\Python\lib\site-packages\tensorflow\python\saved_model\save.py", line 510, in _fill_meta_graph_def
    object_map, resource_map, asset_info = saveable_view.map_resources()
  File "D:\Python\lib\site-packages\tensorflow\python\saved_model\save.py", line 245, in map_resources
    tensor_util.constant_value(capture))
  File "D:\Python\lib\site-packages\tensorflow\python\framework\constant_op.py", line 246, in constant
    allow_broadcast=True)
  File "D:\Python\lib\site-packages\tensorflow\python\framework\constant_op.py", line 284, in _constant_impl
    allow_broadcast=allow_broadcast))
  File "D:\Python\lib\site-packages\tensorflow\python\framework\tensor_util.py", line 454, in make_tensor_proto
    raise ValueError("None values not supported.")
ValueError: None values not supported.

回溯（最近一次呼叫最后一次）：
文件“D:\Python\Threat\u Assesser\retain.py”，第78行，在
tf.saved_model.save（model，saved_model_path）
文件“D:\Python\lib\site packages\tensorflow\Python\saved\u model\save.py”，第822行，保存
元图定义、可保存视图、签名）
文件“D:\Python\lib\site packages\tensorflow\Python\saved\u model\save.py”，第510行，在“填充”元“图形”定义中
对象映射、资源映射、资产信息=可保存的视图。映射资源（）
文件“D:\Python\lib\site packages\tensorflow\Python\saved\u model\save.py”，第245行，在map\u参考资料中
张量常数（捕捉）
文件“D:\Python\lib\site packages\tensorflow\Python\framework\constant\u op.py”，第246行，常量
允许（广播=真）
文件“D:\Python\lib\site packages\tensorflow\Python\framework\constant\u op.py”，第284行，在常量\u impl中
允许广播=允许广播）
文件“D:\Python\lib\site packages\tensorflow\Python\framework\tensor\u util.py”，第454行，在make\u tensor\u proto中
raise VALUERROR（“不支持无值”）
ValueError:不支持任何值。

有人知道这是怎么回事吗

Traceback (most recent call last):
  File "D:\Python\Threat_Assesser\retrain.py", line 78, in <module>
    tf.saved_model.save(model, saved_model_path)
  File "D:\Python\lib\site-packages\tensorflow\python\saved_model\save.py", line 822, in save
    meta_graph_def, saveable_view, signatures)
  File "D:\Python\lib\site-packages\tensorflow\python\saved_model\save.py", line 510, in _fill_meta_graph_def
    object_map, resource_map, asset_info = saveable_view.map_resources()
  File "D:\Python\lib\site-packages\tensorflow\python\saved_model\save.py", line 245, in map_resources
    tensor_util.constant_value(capture))
  File "D:\Python\lib\site-packages\tensorflow\python\framework\constant_op.py", line 246, in constant
    allow_broadcast=True)
  File "D:\Python\lib\site-packages\tensorflow\python\framework\constant_op.py", line 284, in _constant_impl
    allow_broadcast=allow_broadcast))
  File "D:\Python\lib\site-packages\tensorflow\python\framework\tensor_util.py", line 454, in make_tensor_proto
    raise ValueError("None values not supported.")
ValueError: None values not supported.