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: macd_series.go
    path of file: ./repos/go-chart
    
    the code of the file until where you have to start completion: package chart

import "fmt"

const (
	// DefaultMACDPeriodPrimary is the long window.
	DefaultMACDPeriodPrimary = 26
	// DefaultMACDPeriodSecondary is the short window.
	DefaultMACDPeriodSecondary = 12
	// DefaultMACDSignalPeriod is the signal period to compute for the MACD.
	DefaultMACDSignalPeriod = 9
)

// MACDSeries computes the difference b
    
func (macds MACDSignalSeries) GetPeriods() (w1, w2, sig int) {
	if macds.PrimaryPeriod == 0 {
		w1 = DefaultMACDPeriodPrimary
	} else {
		w1 = macds.PrimaryPeriod
	}
	if macds.SecondaryPeriod == 0 {
		w2 = DefaultMACDPeriodSecondary
	} else {
		w2 = macds.SecondaryPeriod
	}
	if macds.SignalPeriod == 0 {
		sig = DefaultMACDSignalPeriod
	} else {
		sig = macds.SignalPeriod
	}
	return
}