string registered in the <a href="https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry">IANA Language Subtag
Registry</a>
with the type "region". The string specified must match the case of the
string in the registry.</p>
<p>Region subtags that are deprecated in the registry and have a preferred
code are changed to their preferred code. For example, <code>const Locale('de',
'DE')</code> and <code>const Locale('de', 'DD')</code> are equal, and both have the
<a href="dart-ui/Loca