How to use the fitter.storage.s3.S3SourceStorage function in fitter

fitter.cache_store = RedisStore(
        fitter.config['CACHE_STORE']['HOST'],
        fitter.config['CACHE_STORE']['PORT'],
        fitter.config['CACHE_STORE']['DB'],
        fitter.config['CACHE_STORE']['PASSWORD'],
    )
elif fitter.config['CACHE_STORE']['TYPE'] == 'in-memory':
    fitter.cache_store = InMemoryStore()

_source_storage_config = fitter.config['SOURCE_STORAGE']
_store_storage_config = fitter.config['STORE_STORAGE']

if _source_storage_config['TYPE'] == 'fs':
    fitter.source_storage = _set_file_system_storage(FileSystemSourceStorage, _source_storage_config)
elif _source_storage_config['TYPE'] == 's3':
    fitter.source_storage = _set_s3_storage(S3SourceStorage, _source_storage_config)

if _store_storage_config['TYPE'] == 'fs':
    fitter.store_storage = _set_file_system_storage(FileSystemStoreStorage, _store_storage_config)
elif _store_storage_config['TYPE'] == 's3':
    fitter.store_storage = _set_s3_storage(S3StoreStorage, _store_storage_config)