code: protected String getUserSegmentName(String segment){
          Matcher m = USER_SEGMENT_PATTERN.matcher(segment);
          if(m.find()){
              String value = m.group(0);
              return value.substring(1, value.length() - 1); //I wish I knew  regexp better!
          }
          return null;
      }
docs: Extracts user segment name from route config. Returns null if no pattern match: {xxx}.
  
  @param segment user segment, such as "{user_id}",  "{fav_color}", etc.
  @return the name inside the braces, "user_id", "fav_color", etc.
  Returns null if no pattern match: {xxx}.