*     FIRST_LETTER_MULTIMAP.put('a', "pple");
   *     FIRST_LETTER_MULTIMAP.put('a', "sparagus");
   *     FIRST_LETTER_MULTIMAP.put('c', "arrot");
   *     FIRST_LETTER_MULTIMAP.put('c', "herry");
   * }
   * }</pre>
   *
   * <p>To collect to an {@link ImmutableMultimap}, use either {@link
   * ImmutableSetMultimap#toImmutableSetMultimap} or {@link
   * ImmutableListMultimap#toImmutableListMultimap}.