}

  /**
   * Explicitly specifies the return type of this {@code Invokable}. For example:
   *
   * {@snippet :
   * Method factoryMethod = Person.class.getMethod("create");
   * Invokable<?, Person> factory = Invokable.of(getNameMethod).returning(Person.class);
   * }
   */
  public final <R1 extends R> Invokable<T, R1> returning(Class<R1> returnType) {
    return returning(TypeToken.of(returnType));
  }

   * b)} is true if and only if {@code equivalence.equivalent(function.apply(a), function.apply(b))}
   * is true.
   *
   * <p>For example:
   *
   * {@snippet :
   * Equivalence<Person> SAME_AGE = Equivalence.equals().onResultOf(GET_PERSON_AGE);
   * }
   *
   * <p>{@code function} will never be invoked with a null value.
   *