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: pr_extractor.go
    path of file: ./repos/incubator-devlake/backend/plugins/github/tasks
    
    the code of the file until where you have to start completion: /*
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements.  See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You 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 tasks

import (
	"encoding/json"
	"regexp"

	"github.com/apache/incubator-devlake/core/errors"
	"github.com/apache/incubator-devlake/core/models/common"
	"github.com/apache/incubator-devlake/core/plugin"
	"github.com/apache/incubator-devlake/helpers/pluginhelper/api"
	"github.com/apache/incubator-devlake/plugins/github/models"
)

func init() {
	RegisterSubtaskMeta(&ExtractApiPullRequestsMeta)
}

var ExtractApiPullRequestsMeta = plugin.SubTaskMeta{
	Name:             "extractApiPullRequests",
	EntryPoint:       ExtractApiPullRequests,
	EnabledByDefault: true,
	Description:      "Extract raw PullRequests data into tool layer table github_pull_requests",
	DomainTypes:      []string{plugin.DOMAIN_TYPE_CROSS, plugin.DOMAIN_TYPE_CODE_REVIEW},
	DependencyTables: []string{RAW_PULL_REQUEST_TABLE},
	ProductTables: []string{
		models.GithubRepoAccount{}.TableName(),
		models.GithubPrLabel{}.TableName(),
		models.GithubPullRequest{}.TableName()},
}

type GithubApiPullRequest struct {
	GithubId int             `json:"id"`
	Number   int             `json:"number"`
	State    string          `json:"state"`
	Title    string          `json:"title"`
	Body     json.RawMessage `json:"body"`
	HtmlUrl  string          `json:"html_url"`
	Labels   []struct {
		Name string `json:"name"`
	} `json:"labels"`
	Assignee        *GithubAccountResponse `json:"assignee"`
	User            *GithubAccountResponse `json:"user"`
	ClosedAt        *common.Iso8601Time    `json:"closed_at"`
	MergedAt        *common.Iso8601Time    `json:"merged_at"`
	GithubCreatedAt common.Iso8601Time     `json:"created_at"`
	GithubUpdatedAt common.Iso8601Time     `json:"updated_at"`
	MergeCommitSha  string                 `json:"merge_commit_sha"`
	Head            struct {
		Ref  string         `json:"ref"`
		Sha  string         `json:"sha"`
		Repo *GithubApiRepo `json:"repo"`
	} `json:"head"`
	Base struct {
		Ref  string         `json:"ref"`
		Sha  
    
func ExtractApiPullRequests(taskCtx plugin.SubTaskContext) errors.Error {
	data := taskCtx.GetData().(*GithubTaskData)
	config := data.Options.ScopeConfig
	var labelTypeRegex *regexp.Regexp
	var labelComponentRegex *regexp.Regexp
	var prType = config.PrType
	var err error
	if len(prType) > 0 {
		labelTypeRegex, err = regexp.Compile(prType)
		if err != nil {
			return errors.Default.Wrap(err, "regexp Compile prType failed")
		}
	}
	var prComponent = config.PrComponent
	if len(prComponent) > 0 {
		labelComponentRegex, err = regexp.Compile(prComponent)
		if err != nil {
			return errors.Default.Wrap(err, "regexp Compile prComponent failed")
		}
	}

	extractor, err := api.NewApiExtractor(api.ApiExtractorArgs{
		RawDataSubTaskArgs: api.RawDataSubTaskArgs{
			Ctx: taskCtx,
			/*
				This struct will be JSONEncoded and stored into database along with raw data itself, to identity minimal
				set of data to be process, for example, we process JiraIssues by Board
			*/
			Params: GithubApiParams{
				ConnectionId: data.Options.ConnectionId,
				Name:         data.Options.Name,
			},
			/*
				Table store raw data
			*/
			Table: RAW_PULL_REQUEST_TABLE,
		},
		Extract: func(row *api.RawData) ([]interface{}, errors.Error) {
			rawL := &GithubApiPullRequest{}
			err := errors.Convert(json.Unmarshal(row.Data, rawL))
			if err != nil {
				return nil, err
			}
			// need to extract 2 kinds of entities here
			results := make([]interface{}, 0, 1)
			if rawL.GithubId == 0 {
				return nil, nil
			}
			//If this is a pr, ignore
			githubPr, err := convertGithubPullRequest(rawL, data.Options.ConnectionId, data.Options.GithubId)
			if err != nil {
				return nil, err
			}
			if rawL.User != nil {
				githubUser, err := convertAccount(rawL.User, data.Options.GithubId, data.Options.ConnectionId)
				if err != nil {
					return nil, err
				}
				results = append(results, githubUser)
				githubPr.AuthorName = githubUser.Login
				githubPr.AuthorId = githubUser.AccountId
			}
			for _, label := range rawL.Labels {
				results = append(results, &models.GithubPrLabel{
					ConnectionId: data.Options.ConnectionId,
					PullId:       githubPr.GithubId,
					LabelName:    label.Name,
				})
				// if pr.Type has not been set and prType is set in .env, process the below
				if labelTypeRegex != nil && labelTypeRegex.MatchString(label.Name) {
					githubPr.Type = label.Name
				}
				// if pr.Component has not been set and prComponent is set in .env, process
				if labelComponentRegex != nil && labelComponentRegex.MatchString(label.Name) {
					githubPr.Component = label.Name
				}
			}
			results = append(results, githubPr)

			return results, nil
		},
	})

	if err != nil {
		return errors.Default.Wrap(err, "error initializing Github PR extractor")
	}

	return extractor.Execute()
}