only add content_type attr if not in attrs list supplied by user
only add content_type attr if not in attrs list supplied by user

smrjan/seldon-server,smrjan/seldon-server,SeldonIO/seldon-server,smrjan/seldon-server,SeldonIO/seldon-server,SeldonIO/seldon-server,SeldonIO/seldon-server,SeldonIO/seldon-server,smrjan/seldon-server,smrjan/seldon-server