def perform_import(val, setting_name):
    if val is None:
        return None
    elif isinstance(val, six.string_types):
        return import_from_string(val, setting_name)
    elif isinstance(val, (list, tuple)):
        return [import_from_string(item, setting_name) for item in val]
    return val
If the given setting is a string import notation,
dataset/ETHPy150Open tomchristie/django-rest-framework/rest_framework/settings.py/perform_import