def test__build_kwargs(self):
        creds = Credentials(aws_secret_access_key='my_key', aws_access_key_id='my_id')
        self.assertDictEqual(creds._build_kwargs(), {
            'aws_secret_access_key': 'my_key',
            'aws_access_key_id': 'my_id'
        })

        creds = Credentials(aws_secret_access_key='my_key', aws_access_key_id='my_id', aws_session_token='my_token')
        self.assertDictEqual(creds._build_kwargs(), {
            'aws_secret_access_key': 'my_key',
            'aws_access_key_id': 'my_id',
            'aws_session_token': 'my_token'
        })