...
def deploy_serverless(logger):
...
    deploy_stage = os.getenv('SERVERLESS_STAGE')
    if deploy_stage is not None:
        call_str = 'serverless deploy -s {0}'.format(deploy_stage)
    else:
        call_str = 'serverless deploy'
    ret = call(call_str, shell=True)
...
def remove(logger):
...
    if deploy_stage is not None:
        call_str = 'serverless remove -s {0}'.format(deploy_stage)
    else:
        call_str = 'serverless remove'
    ret = call(call_str, shell=True)
...