code: public static <K, V> ImmutableListMultimap<K, V> loadMultimap(final CharSource source,
        final Function<String, K> keyFunction, final Function<String, V> valueFunction)
        throws IOException {
      final ImmutableListMultimap.Builder<K, V> ret = ImmutableListMultimap.builder();
      loadMapToSink(source, MapUtils.asMapSink(ret), keyFunction, valueFunction,
          IsCommentLine.INSTANCE);
      return ret.build();
    }
docs: Reads an {@link ImmutableListMultimap} from a {@link CharSource}, where each line is a key, a
  tab character ("\t"), and a value. Blank lines and lines beginning with "#" are ignored.