code: private SequenceType parseSequenceType() {
  
          if (is("empty-sequence", true)) {
              consume(TokenType.OPEN_BR, true);
              consume(TokenType.CLOSE_BR, true);
              return new SequenceType();
  
          } else {
              final AbsFilter filter = parseItemType();
              if (isWildcard()) {
                  final char wildcard = parseOccuranceIndicator();
                  return new SequenceType(filter, wildcard);
              }
              return new SequenceType(filter);
          }
      }
docs: Parses the the rule SequenceType according to the following production
  rule: [
  <p>
  49] SequenceType ::= (ItemType OccurrenceIndicator?) | <"void" "(" ")"> .
  </p>
  
  @return SequenceType