code: @Nonnull
      @Deprecated
      public static <T1, T2> Function<Pair<? extends T1, ? extends T2>, ? extends T1> fst(@Nonnull final Class<T1> clazz) {
          return new First<>();
      }
docs: Makes grabbing the first value out of a collection of Pairs a bit easier, e.g.
  given an iterable over Pair.of(String, ?) objects:
  
  <br>
  <code>... = Iterables.transform(iterable, Pair.fst(String.class))</code>
  
  @param clazz The class type for a.
  @param <T1> Expected data type for {@link Pair#a}
  @param <T2> Expected data type for {@link Pair#b}
  @return a Function that returns null or the first value of the Pair, which also may be null
  @deprecated use {@link #fst()}.