code: void internalAddContractions(int c, UnicodeSet set) {
          new ContractionsAndExpansions(set, null, null, false).forCodePoint(data, c);
      }
docs: Adds the contractions that start with character c to the set.
  Ignores prefixes. Used by AlphabeticIndex.
  @deprecated This API is ICU internal only.
  @hide draft / provisional / internal are hidden on Android