text: -- make sure the prerequisite libraries are loaded
  LOAD 'plpython3';
  SELECT NULL::ltree;
  
  
  CREATE FUNCTION ltree_to_plpython3(val internal) RETURNS internal
  LANGUAGE C STRICT IMMUTABLE
  AS 'MODULE_PATHNAME', 'ltree_to_plpython';
  
  CREATE TRANSFORM FOR ltree LANGUAGE plpython3u (
      FROM SQL WITH FUNCTION ltree_to_plpython3(internal)
  );
  