return getSubMap(0, keySet.headIndex(checkNotNull(toKey), inclusive));
  }

  /**
   * This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys ranges
   * from {@code fromKey}, inclusive, to {@code toKey}, exclusive.
   *
   * <p>The {@link SortedMap#subMap} documentation states that a submap of a submap throws an {@link

    return getSubMap(0, keySet.headIndex(checkNotNull(toKey), inclusive));
  }

  /**
   * This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys ranges
   * from {@code fromKey}, inclusive, to {@code toKey}, exclusive.
   *
   * <p>The {@link SortedMap#subMap} documentation states that a submap of a submap throws an {@link

    }

    @Override
    public boolean matches(char c) {
      return c <= '\u007f';
    }
  }

  /** Implementation that matches characters that fall within multiple ranges. */
  private static class RangesMatcher extends CharMatcher {

    private final String description;
    private final char[] rangeStarts;
    private final char[] rangeEnds;

    }

    @Override
    public boolean matches(char c) {
      return c <= '\u007f';
    }
  }

  /** Implementation that matches characters that fall within multiple ranges. */
  private static class RangesMatcher extends CharMatcher {

    private final String description;
    private final char[] rangeStarts;
    private final char[] rangeEnds;