'Information about this task suitable for on-screen display.'

def info(self, fields=None, extra=[]):

    fields = (self._info_fields if (fields is None) else fields)
    def _keys():
        for key in (list(fields) + list(extra)):
            value = getattr(self, key, None)
            if (value is not None):
                (yield (key, value))
    return dict(_keys())
