Fail to convert to tflite

Hi
I got problem:
Traceback (most recent call last):
File "/content/models/research/object_detection/export_tflite_graph_tf2.py", line 126, in
app.run(main)
File "/usr/local/lib/python3.6/dist-packages/absl/app.py", line 300, in run
_run_main(main, args)
File "/usr/local/lib/python3.6/dist-packages/absl/app.py", line 251, in _run_main
sys.exit(main(argv))
File "/content/models/research/object_detection/export_tflite_graph_tf2.py", line 122, in main
FLAGS.ssd_use_regular_nms)
File "/content/models/research/object_detection/export_tflite_graph_lib_tf2.py", line 231, in export_tflite_model
pipeline_config.model, is_training=False)
File "/content/models/research/object_detection/builders/model_builder.py", line 1090, in build
add_summaries)
File "/content/models/research/object_detection/builders/model_builder.py", line 380, in _build_ssd_model
is_training=is_training)
File "/content/models/research/object_detection/builders/model_builder.py", line 293, in _build_ssd_feature_extractor
feature_extractor_class = SSD_KERAS_FEATURE_EXTRACTOR_CLASS_MAP[
NameError: name 'SSD_KERAS_FEATURE_EXTRACTOR_CLASS_MAP' is not defined

After run below command, can show me how to fix this one

!python /content/models/research/object_detection/export_tflite_graph_tf2.py
--pipeline_config_path /content/data/pipeline.config
--trained_checkpoint_dir /content/output/checkpoint
--output_directory /content/model_android