Howto: add a configuration option

Adding of newer configuration options to existing stages should be relatively straightforward:

1. Open the stage python script that has to be modified (e.g. diffusion : /cmp/stages/diffusion/diffusion.py)

2. Add the configuration option in the _Config Class with it's awaited trait-type (See here for a list of simple types and here for other predefined traits).

3. Modify the traits_view element to incorporate your new property (use 'property_name' if you want to use the default trait editor, else use Item('property_name', editor=...) as described here).

4. Modify the create_workflow method of the <stage_name> Class to take into account your new config option by adding it into the inputs field of one of the processing node (e.g. fsl_flirt.inputs.args = self.config.args)