fail: alter table <table_name> NOCHECK CONSTRAINT ALL;

I have tried:

alter table <table_name> NOCHECK CONSTRAINT ALL;

and it highlights (squiggles) NOCHECK saying : ERROR: syntax error at or
near "NOCHECK" SQL state: 42601 character 20

but everything I lookup says this this is the way to disable all
constraints on a table.

Also is there a way to disable all existing constraints on all tables
everywhere (specifically all pkey & fkey constraints irrespective of how
they were created) in one statement?

I have searched and searched and find nothing that works.

J.V.