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: use_srtp.go
    path of file: ./repos/scan4all/vendor/github.com/pion/dtls/v2/pkg/protocol/extension
    
    the code of the file until where you have to start completion: // SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT

package extension

import "encoding/binary"

const (
	useSRTPHeaderSize = 6
)

// UseSRTP allows a Client/Server to negotiate what SRTPProtectionProfiles
// they both support
//
// https://tools.ietf.org/html/rfc8422
type UseSRTP struct {
	ProtectionProfil
    
func (u *UseSRTP) Marshal() ([]byte, error) {
	out := make([]byte, useSRTPHeaderSize)

	binary.BigEndian.PutUint16(out, uint16(u.TypeValue()))
	binary.BigEndian.PutUint16(out[2:], uint16(2+(len(u.ProtectionProfiles)*2)+ /* MKI Length */ 1))
	binary.BigEndian.PutUint16(out[4:], uint16(len(u.ProtectionProfiles)*2))

	for _, v := range u.ProtectionProfiles {
		out = append(out, []byte{0x00, 0x00}...)
		binary.BigEndian.PutUint16(out[len(out)-2:], uint16(v))
	}

	out = append(out, 0x00) /* MKI Length */
	return out, nil
}