code: func parseFlowSpecNumericOperator(submatch []string) (operator uint8, err error) {
  	if submatch[1] == "&" {
  		operator = DEC_NUM_OP_AND
  	}
  	value, ok := DECNumOpValueMap[submatch[2]]
  	if !ok {
  		return 0, fmt.Errorf("invalid numeric operator: %s%s", submatch[1], submatch[2])
  	}
  	operator |= uint8(value)
  	return operator, nil
  }
docs: // Parses the FlowSpec numeric operator using the given submatch which should be
  // the return value of func (*Regexp) FindStringSubmatch.