Function<? super String, Integer> g = new HashCodeFunction();
    Function<Float, String> f = Functions.forMap(m, "F");

    Function<Float, Boolean> c1 = Functions.compose(Functions.compose(h, g), f);
    Function<Float, Boolean> c2 = Functions.compose(h, Functions.compose(g, f));

    // Might be nice (eventually) to have:
    //     assertEquals(c1, c2);

    // But for now, settle for this:

    Function<? super String, Integer> g = new HashCodeFunction();
    Function<Float, String> f = Functions.forMap(m, "F");

    Function<Float, Boolean> c1 = Functions.compose(Functions.compose(h, g), f);
    Function<Float, Boolean> c2 = Functions.compose(h, Functions.compose(g, f));

    // Might be nice (eventually) to have:
    //     assertEquals(c1, c2);

    // But for now, settle for this:

    new EqualsTester()
        .addEqualityGroup(
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")),
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(2), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("bar")))
        .testEquals();
  }

    new EqualsTester()
        .addEqualityGroup(
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")),
            Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(2), Suppliers.ofInstance("foo")))
        .addEqualityGroup(Suppliers.compose(Functions.constant(1), Suppliers.ofInstance("bar")))
        .testEquals();
  }

    Predicate<String> trimEqualsFoo = Predicates.compose(equalsFoo, trim);
    Function<String, String> identity = Functions.identity();

    assertTrue(trimEqualsFoo.apply("Foo"));
    assertTrue(trimEqualsFoo.apply("   Foo   "));
    assertFalse(trimEqualsFoo.apply("Foo-b-que"));

    new EqualsTester()
        .addEqualityGroup(trimEqualsFoo, Predicates.compose(equalsFoo, trim))
        .addEqualityGroup(equalsFoo)

   * is defined as the function h such that {@code h(a) == g(f(a))} for each {@code a}.
   *
   * <p><b>Java 8+ users:</b> use {@code g.compose(f)} or (probably clearer) {@code f.andThen(g)}
   * instead.
   *
   * @param g the second function to apply
   * @param f the first function to apply
   * @return the composition of {@code f} and {@code g}

   * call {@code supplier} or invoke {@code function} until it is called.
   */
  public static <F extends @Nullable Object, T extends @Nullable Object> Supplier<T> compose(
      Function<? super F, T> function, Supplier<F> supplier) {
    return new SupplierComposition<>(function, supplier);
  }

  private static class SupplierComposition<F extends @Nullable Object, T extends @Nullable Object>

   * predicate returns {@code predicate(function(x))}.
   *
   * @return the composition of the provided function and predicate
   */
  public static <A extends @Nullable Object, B extends @Nullable Object> Predicate<A> compose(
      Predicate<B> predicate, Function<A, ? extends B> function) {
    return new CompositionPredicate<>(predicate, function);
  }

  /**

          @Override
          public boolean removeAll(Collection<?> c) {
            return removeEntryIf(compose(in(c), Maps.<V>valueFunction()));
          }

          @Override
          public boolean retainAll(Collection<?> c) {
            return removeEntryIf(compose(not(in(c)), Maps.<V>valueFunction()));
          }
        };
      }
    }
  }

  @Override

   * is defined as the function h such that {@code h(a) == g(f(a))} for each {@code a}.
   *
   * <p><b>Java 8+ users:</b> use {@code g.compose(f)} or (probably clearer) {@code f.andThen(g)}
   * instead.
   *
   * @param g the second function to apply
   * @param f the first function to apply
   * @return the composition of {@code f} and {@code g}