Improved conversion stability for tensors with None geometry

[PINTO0309]

1. Content and background

• Slice, Gather, Concat
  • Improved conversion stability for tensors with None geometry.
  • Improved transformation stability for models with undefined dimensions.
  • fasterrcnn_resnet50_fpn.onnx
  • https://s3.ap-northeast-2.wasabisys.com/temp-models/onnx2tf_517/fasterrcnn_resnet50_fpn.onnx.tar.gz
    

2. Summary of corrections

3. Before/After (If there is an operating log that can be used as a reference)

4. Issue number (only if there is a related issue)

• ValueError: as_list() is not defined on an unknown TensorShape #1067