don't specify ``dest`` here - you always want this to just default to the long-form parameter name (``cpus`` here). See [here](http://bipy.github.io/qcli/doc/tutorials/creating_a_qcli_based_script.html#guidelines-on-values-that-should-and-should-not-be-set-when-defining-an-option) for discussion of this and related topics.