def METHOD_NAME(self, parent_devpath, child_devpath):
    child_dev = self.add_disk(child_devpath)
    if child_dev is None:
        return
    parent_dev = self.get_dev_by_devpath(parent_devpath)
    if parent_dev is None:
        return
    child_dev.add_parent(parent_dev.devname)
    parent_dev.add_child(child_dev.devname)