How to \ef a function ?

atletx7-reg017:/home/dgauthie[ 120 ] --> dvdbdev
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psql (11.5, server 11.3)
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dvdb=# \df opid.bef_ins_axi_reqs_set_trig;
List of functions
Schema | Name | Result data type | Argument data
types | Type
--------+---------------------------+------------------+---------------------+------
opid | bef_ins_axi_reqs_set_trig | trigger |
| func
(1 row)

dvdb=# \ef opid.bef_ins_axi_reqs_set_trig;
ERROR: function "opid.bef_ins_axi_reqs_set_trig;" does not exist
dvdb=# \ef opid.bef_ins_axi_reqs_set_trig();
ERROR: expected a right parenthesis
dvdb=#

So the function exists with \df but not \ef ?
I get the need to identify the argument list (in case there's >1 with same
name, diff arg list), but '()' doesn't work. Does this have to do with the
returned trigger type ?