docs: public static String parseDescribeStatement(String statement) {
          Matcher matcher = DescribeToken.matcher(statement);
          if (matcher.matches()) {
              String commandWordTerminator = matcher.group(1);
              if (OneWhitespace.matcher(commandWordTerminator).matches()) {
                  String trailings = matcher.group(3) + ";" + matcher.group(4);
                  // In a valid command, both "trailings" groups should be empty.
                  if (trailings.equals(";")) {
                      // Return the subcommand keyword -- possibly a valid one.
                      return matcher.group(2);
                  }
                  // For an invalid form of the command,
                  // return an approximation of the garbage input.
                  return matcher.group(2) + " " + trailings;
              }
              if (commandWordTerminator.equals("") || commandWordTerminator.equals(";")) {
                  return commandWordTerminator; // EOL or ; reached before subcommand
              }
          }
          return null;
      }