code: public boolean isIdentifier(String... values) {
          if (values.length == 0) {
              return is(TokenType.ID);
          }
          for (String value : values) {
              if (matches(TokenType.ID, value)) {
                  return true;
              }
          }
          return false;
      }
docs: Determines if this token is an identifier.
  <p>
  If a list of <tt>values</tt> is given, this method checks that the content matches one of them.
  
  @param values the values to check for. If the list es empty, only the token type is checked.
  @return <tt>true</tt> if this token is an identifier and matches one of the given <tt>values</tt> if the list
  is not empty.