How can I construct a bool constant cs?

[amutu]

I can use cs = cs to get a boolean cs:

crash=> select cs_filter(cs_const(1)=cs_const(1),uin) from crashlog_get(604176597);
NOTICE: IMCS command: const
CONTEXT: PL/pgSQL function cs_const(double precision,cs_elem_type) line 1 at RETURN
NOTICE: IMCS command: const
CONTEXT: PL/pgSQL function cs_const(double precision,cs_elem_type) line 1 at RETURN
NOTICE: IMCS command: eq
NOTICE: IMCS command: filter

                                    cs_filter                                                              

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int8:{1824680521,2619036035,1824680521,2115425441,1824680521,1824680521,2861741560,2516178417,1824680521,18246
80521,2861741560,1824680521,2606780563,1824680521,1824680521,1301356009,1824680521,2134037263,1824680521,246749
4502,1824680521,1824680521,1824680521,2861741560,1646011213,1647899823,2878643443,1824680521,2367894140,1240925

but I want to use the cs_const function to construct,now is failed:
crash=> select cs_filter(cs_parse('t','bool'),uin) from crashlog_get(604176597);
NOTICE: IMCS command: parse
CONTEXT: PL/pgSQL function cs_parse(text,cs_elem_type,integer) line 1 at RETURN
NOTICE: IMCS command: parse
CONTEXT: PL/pgSQL function cs_parse(text,cs_elem_type,integer) line 1 at RETURN
NOTICE: IMCS command: filter
ERROR: invalid input format of timeseries literal t
crash=> select cs_filter(cs_const('t'::boolean),uin) from crashlog_get(604176597);
ERROR: function cs_const(boolean) does not exist
LINE 1: select cs_filter(cs_const('t'::boolean),uin) from crashlog_g...