ARTIQ type of core devices

FENIX

I met a problem when I wrote the followed lines of codes:

from artiq.coredevice.core import Core
from artiq.coredevice.zotino import Zotino
from artiq.experiment import *


class ExampleCode(EnvExperiment):

    def build(self):
        # The host process some arguments and add some handler to the followed list
        # the list may or may not be empty
        self.deviceList = []
        self.deviceLength: int = len(self.deviceList)

    @kernel
    def run(self):
        # I placed some core device action here.
        # with the followed line, I could raise "Type can't not be fully inferred" error
        for i in range(self.deviceLength):
            deviceHandler = self.deviceList[i]

If a variable request a member of a list which may be or may not be empty, it would raise type annotation error when the code is executed with this list is empty. I tried to explicitly mark its type(such as: Zotino AD53XX or AD9910), and I found that it won't work because these are not belong to ARTIQ types.

So here I would like to request some tips for the followed questions:

How ARTIQ actually process a "Device" type when "Device" type is not an ARTIQ type
How may I explicitly infer a variable to be "Zotino" type or some other core device type, instead of leave it
to be infered by the complier

Thank you for your help in advance