code: public static <T1, T2, T3, R> FluentFunctions.FluentTriFunction<T1, T2, T3, R> of(final Function3<T1, T2, T3, R> fn) {
          return new FluentTriFunction<>(
                                         fn);
      }
docs: Convert a CheckedTriFunction to a FluentTriFunction
  <pre>
  {@code
  FluentFunctions.of(this::add)
  .matches(-1,c->c.hasValues(3).applyHKT(i->3))
  .applyHKT(1,1,1)
  }
  </pre>
  @param fn TriFunction to convert
  @return FluentTriFunction