It resolved! I modified the code to this
# instead of spec = model_spec.get('efficientdet_lite0')

spec = object_detector.EfficientDetSpec(
  model_name='efficientdet-lite0', 
  uri='https://tfhub.dev/tensorflow/efficientdet/lite0/feature-vector/1', 
  hparams={'max_instances_per_image': 8000})

That pass the hyperparameters directly and this worked successfully