How to use the nmslib.DataType.OBJECT_AS_STRING function in nmslib

def test_object_as_string_fresh(batch=True):
    space_type = 'cosinesimil'
    space_param = []
    method_name = 'small_world_rand'
    index_name  = method_name + '.index'
    if os.path.isfile(index_name):
        os.remove(index_name)
    index = nmslib.init(
                             space_type,
                             space_param,
                             method_name,
                             nmslib.DataType.OBJECT_AS_STRING,
                             nmslib.DistType.FLOAT)

    if batch:
        data = [s for s in read_data_as_string('sample_dataset.txt')]
        positions = nmslib.addDataPointBatch(index, np.arange(len(data), dtype=np.int32), data)
    else:
        for id, data in enumerate(read_data_as_string('sample_dataset.txt')):
            nmslib.addDataPoint(index, id, data)

    print('Let\'s print a few data entries')
    print('We have added %d data points' % nmslib.getDataPointQty(index))

    for i in range(0,min(MAX_PRINT_QTY,nmslib.getDataPointQty(index))):
       print(nmslib.getDataPoint(index, i))

    print('Let\'s invoke the index-build process')

def setUp(self):
        space_type = 'normleven'
        space_param = []
        method_name = 'small_world_rand'
        index_name  = method_name + '.index'
        if os.path.isfile(index_name):
            os.remove(index_name)
        self.index = nmslib.init(
                             space_type,
                             space_param,
                             method_name,
                             nmslib.DataType.OBJECT_AS_STRING,
                             nmslib.DistType.FLOAT)

k = 3

    for idx, data in enumerate(read_data_as_string('sample_queryset.txt')):
        print(idx, nmslib.knnQuery(index, k, data))

    nmslib.saveIndex(index, index_name)

    print("The index %s is saved" % index_name)

    nmslib.freeIndex(index)

if __name__ == '__main__':

    print('DENSE_VECTOR', nmslib.DataType.DENSE_VECTOR)
    print('SPARSE_VECTOR', nmslib.DataType.SPARSE_VECTOR)
    print('OBJECT_AS_STRING', nmslib.DataType.OBJECT_AS_STRING)

    print('DistType.INT', nmslib.DistType.INT)
    print('DistType.FLOAT', nmslib.DistType.FLOAT)


    test_vector_load()

    test_vector_fresh()
    test_vector_fresh(False)
    test_vector_loaded()

    gen_sparse_data()
    test_sparse_vector_fresh()

    test_string_fresh()
    test_string_fresh(False)