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: quarter.go
    path of file: ./repos/ferret/pkg/stdlib/datetime
    
    the code of the file until where you have to start completion: package datetime

import (
	"context"
	"time"

	"github.com/MontFerret/ferret/pkg/runtime/core"
	"github.com/MontFerret/ferret/pkg/runtime/values"
	"github.com/MontFerret/ferret/pkg/runtime/values/types"
)

// DATE_QUARTER returns which quarter date belongs to.
// @param {DateTime} date - Source DateTime.
// @return {Int} - A quarter number.
func DateQuarter(_ context.Context, args ...core.Value) (core.Value, error) {
	err := core.ValidateArgs(args, 1, 1)
	if err != nil {
		return values.None, err
	}

	err = core.ValidateType(args[0], types.DateTime)
	if err != nil 
    
func DateQuarter(_ context.Context, args ...core.Value) (core.Value, error) {
	err := core.ValidateArgs(args, 1, 1)
	if err != nil {
		return values.None, err
	}

	err = core.ValidateType(args[0], types.DateTime)
	if err != nil {
		return values.None, err
	}

	month := args[0].(values.DateTime).Month()
	quarter := values.NewInt(1)

	switch month {
	case time.April, time.May, time.June:
		quarter = values.NewInt(2)
	case time.July, time.August, time.September:
		quarter = values.NewInt(3)
	case time.October, time.November, time.December:
		quarter = values.NewInt(4)
	}

	return quarter, nil
}