@Override
  public TextContent trimWhitespace() {
    String text = toString();
    int start = 0;
    int end = text.length();
    while (start < end && isSpace(text, start)) start++;
    while (start < end && isSpace(text, end - 1)) end--;
    if (start >= end) {
      return null;
    }
    if (start > 0 || end < text.length()) {
      return excludeRange(new TextRange(end, text.length())).excludeRange(new TextRange(0, start));
    }
    return this;
  }
@Override
  public TextContent trimWhitespace()