Understanding Python Tensorflow-gpu Processor Multiple Specifications

Python introduces Tensorflow-gpu and would like to compute simultaneously with multiple GPUs.

keras.utils.training_utils
of
multi_gpu_model(model,gpus=gpu_count)

Verified that multiple GPUs can be calculated by running .

Next, I would like to specify which GPU to use.
If you only specify one GPU, I think you can specify which GPU to use in the following code:

with tf.device("/gpu:●"):

If I want to use two GPUs in parallel out of three or more GPUs this time, what should I do?
For example, if you want to use only gpu:0,3 in some parts of the program and gpu:0,3

with tf.device(["/gpu:0", "/gpu:3"]):

I would like to do so.(The above is an image and this code doesn't work)
Is it possible to specify multiple GPUs in this way?
Thank you for your cooperation.