'Set to -1 the extruder field of the spool item currently on.'

def unload(self, extruder):

    spool_item = self._findByColumn(extruder, 2)
    if (spool_item != (-1)):
        self.remove(spool_item[0])
        self._spool_list.append([spool_item[0], spool_item[1], (-1)])
        self._save()
