function toolkit_experimental.unnest(toolkit_experimental.timeseries) does not exist

Relevant system information:

OS: Alpine Linux (I think, using docker image timescale/timescaledb-ha:pg13.4-ts2.4.2-p0)
PostgreSQL version (output of SELECT version();): PostgreSQL 13.4 (Ubuntu 13.4-1.pgdg21.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 10.3.0-1ubuntu1) 10.3.0, 64-bit
TimescaleDB Toolkit version (output of \dx timescaledb_toolkit in psql): 1.2
Installation method: docker

Describe the bug The unnest function doesn't exist or does not work with the timeseries type. In the docs it shows this as timevector not timeseries. Maybe this is my issue?

To Reproduce Follow directions here https://github.com/timescale/timescaledb-toolkit/blob/main/docs/lttb.md#api

DROP TABLE IF EXISTS sample_data;
SET TIME ZONE 'UTC';
CREATE TABLE sample_data(time TIMESTAMPTZ, val DOUBLE PRECISION);
INSERT INTO sample_data
    SELECT
        '2020-01-01 UTC'::TIMESTAMPTZ + make_interval(days=>(foo*10)::int) as time,
        10 + 5 * cos(foo) as val
    FROM generate_series(1,11,0.1) foo;
SELECT time, value::numeric(10,2)
FROM toolkit_experimental.unnest((
    SELECT toolkit_experimental.lttb(time, val, 34)
    FROM sample_data));

Expected behavior 34 records are returned, with 2 columns: time and value.

Actual behavior

ERROR:  42883: function toolkit_experimental.unnest(toolkit_experimental.timeseries) does not exist
LINE 2: FROM toolkit_experimental.unnest((
             ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
LOCATION:  ParseFuncOrColumn, parse_func.c:620

timescale / timescaledb-toolkit

function toolkit_experimental.unnest(toolkit_experimental.timeseries) does not exist #355