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: sync.go
    path of file: ./repos/gapid/gapis/api/sync
    
    the code of the file until where you have to start completion: // Copyright (C) 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package sync provides interfaces for managing externally synchronized APIs.
//
// The methods allow queries to be performed on an API to allow
// the determination of where blocking operations between threads
// of execution happen. These methods allow us to reason about
// execution in a non-linear way.
package sync

import (
	"context"
	"fmt"

	"github.com/google/gapid/core/app/status"
	"github.com/google/gapid/gapis/api"
	"github.com/google/gapid/gapis/api/transform"
	"github.com/google/gapid/gapis/capture"
	"github.com/google/gapid/gapis/service/path"
)

// NoMECSubcommandsError is used to notify the caller that this API does not
// support MEC subcommands.
type NoMECSubcommandsError struct{}

func (e NoMECSubcommandsError) Error() string {
	return "This api does not have MEC subcommands"
}

// SynchronizedAPI defines an API that explicitly has multiple threads of
// execution. This means that replays are not necessarily linear in terms
// of commands.
type SynchronizedAPI interface {
	// GetTerminator returns a transform that wi
    
func MutationCmdsFor(ctx context.Context, c *path.Capture, data *Data, cmds []api.Cmd, id api.CmdID, subindex api.SubCmdIdx, initialCall bool) ([]api.Cmd, error) {
	// This is where we want to handle sub-states
	// This involves transforming the tree for the given Indices, and
	//   then mutating that.
	rc, err := capture.ResolveGraphicsFromPath(ctx, c)
	if err != nil {
		return nil, err
	}

	fullCommand := api.SubCmdIdx{uint64(id)}
	fullCommand = append(fullCommand, subindex...)

	lastCmd := cmds[len(cmds)-1]
	if api.CmdID(len(cmds)) > id {
		lastCmd = cmds[id]
	}

	if sync, ok := lastCmd.API().(SynchronizedAPI); ok {
		// For Vulkan, when preparing the mutation for memory view, we need to get
		// the initial call ID for the requesting subcommand.
		if flattenIdx, ok := sync.FlattenSubcommandIdx(fullCommand, data, initialCall); ok {
			id = flattenIdx
			subindex = api.SubCmdIdx{}
		}
	}

	terminators := make([]transform.Terminator, 0)
	transforms := transform.Transforms{}
	isTrivial := true
	for _, api := range rc.APIs {
		if sync, ok := api.(SynchronizedAPI); ok {
			term, err := sync.GetTerminator(ctx, c)
			if err != nil {
				return nil, err
			}

			t, err := sync.IsTrivialTerminator(ctx, c, fullCommand)
			if err != nil {
				return nil, err
			}
			isTrivial = t && isTrivial
			if term != nil {
				terminators = append(terminators, term)
				continue
			}
		}
		terminators = append(terminators, transform.NewEarlyTerminator(api.ID()))
	}
	for _, t := range terminators {
		if err := t.Add(ctx, id, subindex); err != nil {
			return nil, err
		}
		transforms.Add(t)
	}
	if isTrivial {
		return cmds[0 : id+1], nil
	}
	w := &writer{rc.NewState(ctx), nil}
	if err := transforms.TransformAll(ctx, cmds, 0, w); err != nil {
		return nil, err
	}

	return w.cmds, nil
}