How to do inference on custom dataset ?

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D-ML/issues).
- [X] I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

Hi,
I captured a point cloud and I would like to feed it as the test dataset to SparseconvUnet. can you help me with this issue? how is it possible to see the inference on the custom dataset which is fed as a test dataset to the pre-trained model?