function actionHash(action) {
    // some sort of hashable key for this action
    // action itself cannot be a key in actionConflicts
    // I think getName() (join of optionStrings) is unique enough
    return action.getName();
  }
ArgumentParser#parseKnownArgs(args, namespace) -> array
- args (array): input options
- namespace (Namespace|Object): result object

Parse known arguments and return tuple of result object
and unknown args

See also [original guide][1]

[1]:http://docs.python.org/dev/library/argparse.html#partial-parsing