PLPGSQL Drop all NOT NULL constraints

do $$
    declare r record;
    declare t record;
begin
    for t in select table_name 
             from information_schema.tables 
             where table_schema='public'
    loop
        for r in select a.attname
             from pg_catalog.pg_attribute a
             where attrelid = quote_ident(t.table_name)::regclass
                     and a.attnum > 0
                     and not a.attisdropped
                     and a.attnotnull
        loop
            if quote_ident(r.attname) = 'id' then
                    continue;
            end if;
            execute 'alter table ' || quote_ident(t.table_name) || ' alter ' || quote_ident(r.attname) || ' drop not null;';
        end loop;
    end loop;
end $$;
`