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: naf.go
    path of file: ./repos/gnark/std/math/bits
    
    the code of the file until where you have to start completion: package bits

import (
	"math/big"

	"github.com/consensys/gnark/frontend"
)

// ToNAF returns the NAF decomposition of given input.
// The non-adjacent form (NAF) of a number is a unique signed-digit representation,
// in which non-zero values cannot be adjacent. For example, NAF(13) = [1, 0, -1, 0, 1].
func ToNAF(api frontend.API, v frontend.Variable, opts ...BaseConversionOption) []frontend.Variable {
	// parse options
	cfg := ba
    
func ToNAF(api frontend.API, v frontend.Variable, opts ...BaseConversionOption) []frontend.Variable {
	// parse options
	cfg := baseConversionConfig{
		NbDigits:             api.Compiler().FieldBitLen(),
		UnconstrainedOutputs: false,
	}

	for _, o := range opts {
		if err := o(&cfg); err != nil {
			panic(err)
		}
	}

	c := big.NewInt(1)

	bits, err := api.Compiler().NewHint(nNaf, cfg.NbDigits, v)
	if err != nil {
		panic(err)
	}

	var Σbi frontend.Variable
	Σbi = 0
	for i := 0; i < cfg.NbDigits; i++ {
		Σbi = api.Add(Σbi, api.Mul(bits[i], c))
		c.Lsh(c, 1)
		if !cfg.UnconstrainedOutputs {
			// b * (1 - b) * (1 + b) == 0
			// TODO this adds 3 constraint, not 2. Need api.Compiler().AddConstraint(...)
			b := bits[i]
			y := api.Mul(api.Sub(1, b), api.Add(1, b))
			api.AssertIsEqual(api.Mul(b, y), 0)
		}
	}

	// record the constraint Σ (2**i * b[i]) == v
	api.AssertIsEqual(Σbi, v)

	return bits
}