Does dask-cloudprovider support private dockerhub images?

Does dask-cloudprovider support private docker-hub images (or AWS Elastic Container Registry/ECS)? I tried with no joy:

```python
import dask_cloudprovider
from dask_cloudprovider import FargateCluster
dask_cloudprovider.__version__ # 0.2.0

cluster = FargateCluster(cloudwatch_logs_group="my_log_group",
cluster_name_template='test',
scheduler_timeout="1 hour",
security_groups=["A CUSTOM SECURITY GROUP"],
n_workers=1,
image="asmith26/test-dask_cloudprovider", # points to a private dockerhub (works when made public)
)
```

[UPDATED following @martindurant comment, good idea, many thanks :)]