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: encoder.go
    path of file: ./repos/yq/pkg/yqlib
    
    the code of the file until where you have to start completion: package yqlib

import (
	"io"
)

type Encoder interface {
	Encode(writer io.Writer, node *CandidateNode) error
	PrintDocumentSeparator(writer io.Writer) error
	PrintLeadingContent(writer io.Write
    
func mapKeysToStrings(node *CandidateNode) {

	if node.Kind == MappingNode {
		for index, child := range node.Content {
			if index%2 == 0 { // its a map key
				child.Tag = "!!str"
			}
		}
	}

	for _, child := range node.Content {
		mapKeysToStrings(child)
	}
}