Multithreaded work items
If a work item uses threading, the number of threads for each work item
can simply be specified by using the --cpus-per-task option, similar
to a regular Slurm job.
If you need to know the number of threads in your Slurm job script,
you can use the SLURM_CPUS_PER_TASK_HET_GROUP_0 environment variable.
This variable has to be used, rather than SLURM_CPUS_PER_TASK, because
under the hood, worker-ng uses a heterogeneous job.