SQL::Schema::toymodel holds model specific functions and nuke
$args->{query} parameters.

define add( $addr ) and delete( $addr ) method

IO::MapAdapter->new() accpets two parameters, $map and the parameters
$map_params.
my $obj = new IO::MapAdapter ('mysql:toymodel', $map_params);
where $map_params = { config => {},  query => {} };

move model specific part to SQL::Schema class
remove IO::Adapter::MySQL class