Read list of models and returns a Root object with the proper models added.

def _get_root_object(models):
    '''
    Read list of models and returns a Root object with the proper models added.
    '''
    root = napalm_yang.base.Root()
    for model in models:
        current = napalm_yang
        for part in model.split('.'):
            current = getattr(current, part)
        root.add_model(current)
    return root