"NameError: name 'command' is not defined" when running ImageJ jython script headless

```
Traceback (most recent call last):
File "/home/markemus/dev/pix2pix/stardist_imagej_script.py", line 52, in
res = command.run(StarDist2D, False, "input", imp, "modelChoice", "Versatile (H&E nuclei)",).get()
NameError: name 'command' is not defined
```
The script includes the services:
```
#@ DatasetIOService io
#@ CommandService command
```
and runs successfully when it's run from the ImageJ gui. Do services not work in headless mode? Is there an alternative to using `command` to run StarDist2D, or another way to import it?

EDIT: The command I'm calling is: `./ImageJ-linux64 --headless --jython ~/dev/pix2pix/stardist_imagej_script.py`

Start with stardist_imagej_script.py at line 52 and reproduce the documented ./ImageJ-linux64 --headless --jython invocation. Compare how the @ CommandService command is injected in the GUI and headless modes, then verify that the headless script can invoke StarDist2D without the NameError.

Written by the indexing model from the issue text.