keras/src/backend/torch/core.py/_parse_device_input
def _parse_device_input(device_name):
    if isinstance(device_name, str):
        # We support string value like "cpu:0", "gpu:1", and need to convert
        # "gpu" to "cuda"
        device_name = device_name.lower()
        if "gpu" in device_name:
            device_name = device_name.replace("gpu", "cuda")
    else:
        raise ValueError(
            "Invalid value for argument `device_name`. "
            "Expected a string like 'gpu:0' or 'cpu'. "
            f"Received: device_name='{device_name}'"
        )
    # The torch.Device instance can be used directly.
    return device_name