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: dict.go
    path of file: ./repos/jennifer/jen
    
    the code of the file until where you have to start completion: package jen

import (
	"bytes"
	"io"
	"sort"
)

// Dict renders as key/value pairs. Use with Values for map or composite
// literals.
type Dict map[Code]Code

// DictFunc executes a func(Dict) to generate the value
    
func (d Dict) isNull(f *File) bool {
	if d == nil || len(d) == 0 {
		return true
	}
	for k, v := range d {
		if !k.isNull(f) && !v.isNull(f) {
			// if any of the key/value pairs are both not null, the Dict is not
			// null
			return false
		}
	}
	return true
}