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: selector.go
    path of file: ./repos/cf-tool/vendor/github.com/andybalholm/cascadia
    
    the code of the file until where you have to start completion: package cascadia

import (
	"bytes"
	"fmt"
	"regexp"
	"strings"

	"golang.org/x/net/html"
)

// the Selector type, and functions for creating them

// A Selector is a function which tells whether a node matches or not.
type Selector func(*html.Node) bool

// hasChildMatch returns whether n has any child that matches a.
func hasChildMatch(n *html.Node, a Selector) bool {
	for c := n.FirstChild; c != nil; c = c.Ne
    
func onlyChildSelector(ofType bool) Selector {
	return func(n *html.Node) bool {
		if n.Type != html.ElementNode {
			return false
		}

		parent := n.Parent
		if parent == nil {
			return false
		}

		if parent.Type == html.DocumentNode {
			return false
		}

		count := 0
		for c := parent.FirstChild; c != nil; c = c.NextSibling {
			if (c.Type != html.ElementNode) || (ofType && c.Data != n.Data) {
				continue
			}
			count++
			if count > 1 {
				return false
			}
		}

		return count == 1
	}
}