Recursive function that receives a list of IDs and returns all child IDs

hello pgsql fans out there,

i've already created a function that returns a list of IDs of all sub-samples based on a given sample ID. this works fine. now i like to extend this function so that it can receive a list of sample IDs. e.g.:

fn_get_subsamples(IN sample_numbers SETOF integer)

here is the existing function:

CREATE OR REPLACE FUNCTION fn_get_subsamples(IN sample_number integer)
RETURNS SETOF integer AS
$BODY$
WITH RECURSIVE recursetree(sample_number) AS (
SELECT sample_number
FROM sample
WHERE parent_sample = $1

UNION ALL

SELECT t.sample_number
FROM sample t
JOIN recursetree rt ON rt.sample_number = t.parent_sample
)

SELECT sample_number
FROM recursetree;
$BODY$
LANGUAGE sql VOLATILE

thanks a lot for every hint!
sven
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