Where to define alternative names?

[mihalt]

For example I want to find Czech language by code cz in get_by_code. But it has just this names
iso = {str} 'cs'
iso_639_1 = {str} 'cs'
iso_639_2B = {str} 'cze'
iso_639_2T = {str} 'ces'
iso_639_3 = {str} 'ces'