Dynamically create 'all' group.

def obtain_all_devices(my_devices):
    """Dynamically create 'all' group."""
    new_devices = {}
    for device_name, device_or_group in my_devices.items():
        # Skip any groups
        if not isinstance(device_or_group, list):
            new_devices[device_name] = device_or_group
    return new_devices