code: function localizeStrict( i18nValue, optionalFallbackValue, languageTag = tags[ locale ] ) {
           if( !i18nValue || primitives[ typeof i18nValue ] ) {
              // value is not internationalized
              return i18nValue;
           }
           if( !languageTag ) {
              return optionalFallbackValue;
           }
  
           // Try one direct lookup before scanning the input keys,
           // assuming that language-tags are written in consistent style.
           const value = i18nValue[ languageTag ];
           if( value !== undefined ) {
              return value;
           }
  
           const lookupKey = normalize( languageTag );
           const availableTags = Object.keys( i18nValue );
           const n = availableTags.length;
           for( let i = 0; i < n; ++i ) {
              const t = availableTags[ i ];
              if( normalize( t ) === lookupKey ) {
                 return i18nValue[ t ];
              }
           }
  
           return optionalFallbackValue;
        }
docs: //////////////////////////////////////////////////////////////////////////////////////////////////////