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: unmarshal.go
    path of file: ./repos/plumber/vendor/github.com/aws/aws-sdk-go/private/protocol/rest
    
    the code of the file until where you have to start completion: package rest

import (
	"bytes"
	"encoding/base64"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"reflect"
	"strconv"
	"strings"
	"time"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/request"
	awsStrings "github.com/aws/aws-sdk-go/internal/strings"
	"github.com/aws/aws-sdk-go/private/protocol"
)

// UnmarshalHandler is a named request handler for unmarshaling rest protocol requests
var Unmars
    
func unmarshalHeaderMap(r reflect.Value, headers http.Header, prefix string, normalize bool) error {
	if len(headers) == 0 {
		return nil
	}
	switch r.Interface().(type) {
	case map[string]*string: // we only support string map value types
		out := map[string]*string{}
		for k, v := range headers {
			if awsStrings.HasPrefixFold(k, prefix) {
				if normalize == true {
					k = strings.ToLower(k)
				} else {
					k = http.CanonicalHeaderKey(k)
				}
				out[k[len(prefix):]] = &v[0]
			}
		}
		if len(out) != 0 {
			r.Set(reflect.ValueOf(out))
		}

	}
	return nil
}