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: collaboration.go
    path of file: ./repos/gitea/services/repository
    
    the code of the file until where you have to start completion: // Copyright 2016 The Gogs Authors. All rights reserved.
// Copyright 2020 The Gitea Authors.
// SPDX-License-Identifier: MIT

package repository

import (
	"context
    
func DeleteCollaboration(ctx context.Context, repo *repo_model.Repository, collaborator *user_model.User) (err error) {
	collaboration := &repo_model.Collaboration{
		RepoID: repo.ID,
		UserID: collaborator.ID,
	}

	ctx, committer, err := db.TxContext(ctx)
	if err != nil {
		return err
	}
	defer committer.Close()

	if has, err := db.GetEngine(ctx).Delete(collaboration); err != nil {
		return err
	} else if has == 0 {
		return committer.Commit()
	}

	if err := repo.LoadOwner(ctx); err != nil {
		return err
	}

	if err = access_model.RecalculateAccesses(ctx, repo); err != nil {
		return err
	}

	if err = repo_model.WatchRepo(ctx, collaborator, repo, false); err != nil {
		return err
	}

	if err = models.ReconsiderWatches(ctx, repo, collaborator); err != nil {
		return err
	}

	// Unassign a user from any issue (s)he has been assigned to in the repository
	if err := models.ReconsiderRepoIssuesAssignee(ctx, repo, collaborator); err != nil {
		return err
	}

	return committer.Commit()
}