code: def _get_system_ps(b, item, context='component'):
      
      # TODO: make this a decorator?
      if isinstance(item, list) and len(item)==1:
          item = item[0]
  
      if isinstance(item, ParameterSet):
          return item.filter(context=context, check_visible=False)
      elif isinstance(item, str):
          return b.filter(item, context=context, check_visible=False)
      else:
          logger.debug("_get_system_ps got {}".format(item))
          raise NotImplementedError("_get_system_ps does not support item with type: {}".format(type(item)))
docs: parses the input arg (either twig or PS) to retrieve the actual parametersets