docs: function localizeRelaxed( languageTag, i18nValue, optionalFallback ) {
        assert( languageTag ).hasType( String );
        if( !i18nValue || primitives[ typeof i18nValue ] ) {
           // Value is not i18n (app does not use it)
           return i18nValue;
        }
  
        const tagParts = languageTag ? languageTag.replace( /-/g, '_' ).split( '_' ) : [];
        while( tagParts.length > 0 ) {
           const currentLocaleTag = tagParts.join( '-' );
           const value = localizeStrict( currentLocaleTag, i18nValue );
           if( value !== undefined ) {
              return value;
           }
           tagParts.pop();
        }
  
        if( fallbackTag === undefined ) {
           fallbackTag = configuration.get( 'i18n.fallback' );
        }
  
        return ( fallbackTag && localizeStrict( fallbackTag, i18nValue ) ) || optionalFallback;
     }