You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: css.go
    path of file: ./repos/inbucket/pkg/webui/sanitize
    
    the code of the file until where you have to start completion: package sanitize

import (
	"bytes"
	"strings"

	"github.com/gorilla/css/scanner"
)

// propertyRule may someday allow control of what values are valid for a par
    
func stateValid(b *bytes.Buffer, t *scanner.Token) stateHandler {
	state := stateValid
	if t.Type == scanner.TokenChar && t.Value == ";" {
		// End of property.
		state = stateStart
	}
	b.WriteString(t.Value)
	return state
}