Nvidia-docker error message "volume name is too short"

Accelerated Computing NGC GPU Cloud Docker and NVIDIA Docker
1

Hi
How can I resolve the following error?

$ ls
Dockerfile  download_dataset.sh  pytorch  README.md  run_and_time.sh
$ docker images
REPOSITORY                TAG                                 IMAGE ID       CREATED          SIZE
mlperf/object_detection   latest                              2ac2027d51b4   25 seconds ago   14.7GB
$ nvidia-docker run -v .:/workspace -t -i --rm --ipc=host mlperf/object_detection
docker: Error response from daemon: create .: volume name is too short, names should be at least two alphanumeric characters.
See 'docker run --help'.