Determining if an hstore is empty

What's the canonical way of doing this? Various failed attempts include:

select array_length(%%'a=>1'::hstore -  'a=>1'::hstore, 1)

select array_length(%%('a=>1'::hstore -  'a=>1'::hstore), 1)

select array_length(avals('a=>1'::hstore -  'a=>1'::hstore), 1);

select array_length(akeys('a=>1'::hstore -  'a=>1'::hstore), 1);

select skeys('a=>1'::hstore -  'a=>1'::hstore) is null

select 'a=>1'::hstore -  'a=>1'::hstore is null

Etc.

--
Wells Oliver
wellsoliver@gmail.com