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: tl_contacts_contacts_gen.go
    path of file: ./repos/td/tg
    
    the code of the file until where you have to start completion: // Code generated by gotdgen, DO NOT EDIT.

package tg

import (
	"context"
	"errors"
	"fmt"
	"sort"
	"strings"

	"go.ub
    
func DecodeContactsContacts(buf *bin.Buffer) (ContactsContactsClass, error) {
	id, err := buf.PeekID()
	if err != nil {
		return nil, err
	}
	switch id {
	case ContactsContactsNotModifiedTypeID:
		// Decoding contacts.contactsNotModified#b74ba9d2.
		v := ContactsContactsNotModified{}
		if err := v.Decode(buf); err != nil {
			return nil, fmt.Errorf("unable to decode ContactsContactsClass: %w", err)
		}
		return &v, nil
	case ContactsContactsTypeID:
		// Decoding contacts.contacts#eae87e42.
		v := ContactsContacts{}
		if err := v.Decode(buf); err != nil {
			return nil, fmt.Errorf("unable to decode ContactsContactsClass: %w", err)
		}
		return &v, nil
	default:
		return nil, fmt.Errorf("unable to decode ContactsContactsClass: %w", bin.NewUnexpectedID(id))
	}
}