Download backbone weights from TF Keras pretrained models repository to a directory and provide that path in configuration.

wget https://github.com/keras-team/keras-applications/releases/download/resnet/resnet50_weights_tf_dim_ordering_tf_kernels_notop.h5

If you use a backbone that has been trained by AWS team then you can download TensorFlow SavedModel format models from the following S3 location:

aws s3 cp s3://mzanur-data/models weights --recursive