def _get_gucs(self) -> CaseInsensitiveSet:
        """Get all available GUCs based on ``postgres --describe-config`` output.

        :returns: all available GUCs in the local Postgres server.
        """
        cmd = [self.pgcommand('postgres'), '--describe-config']
        return CaseInsensitiveSet({
            line.split('\t')[0] for line in subprocess.check_output(cmd).decode('utf-8').strip().split('\n')
        })
Get all available GUCs based on ``postgres --describe-config`` output.

        :returns: all available GUCs in the local Postgres server.
        
patroni/postgresql/__init__.py