fix plotting and correct typos (#1060)

Signed-off-by: Mingxin Zheng
<[email protected]>

Fixes #1059 

### Description

- Make the plotting compatible with 3D image label map and one-hot
encoding formats.
- Fix typos and improve some wording.

### Checks
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Notebook runs automatically `./runner [-p <regex_pattern>]`

Signed-off-by: Mingxin Zheng <[email protected]>

Author: mingxin-zheng