code: func parseWhereArgs(args ...interface{}) (mv reflect.Value, op string, err error) {
  	switch len(args) {
  	case 1:
  		mv = reflect.ValueOf(args[0])
  	case 2:
  		var ok bool
  		if op, ok = args[0].(string); !ok {
  			err = errors.New("operator argument must be string type")
  			return
  		}
  		op = strings.TrimSpace(strings.ToLower(op))
  		mv = reflect.ValueOf(args[1])
  	default:
  		err = errors.New("can't evaluate the array by no match argument or more than or equal to two arguments")
  	}
  	return
  }
docs: // parseWhereArgs parses the end arguments to the where function.  Return a
  // match value and an operator, if one is defined.