code: func asLiteral(v interface{}) Literal {
  	switch v := v.(type) {
  	case bool:
  		return &BooleanLiteral{Val: v}
  	case time.Duration:
  		return &DurationLiteral{Val: v}
  	case float64:
  		return &NumberLiteral{Val: v}
  	case int64:
  		return &IntegerLiteral{Val: v}
  	case string:
  		return &StringLiteral{Val: v}
  	case time.Time:
  		return &TimeLiteral{Val: v}
  	default:
  		return &NilLiteral{}
  	}
  }
docs: // asLiteral takes an interface and converts it into an influxql literal.