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: api.explain.go
    path of file: ./repos/corteza/extra/server-discovery/vendor/github.com/elastic/go-elasticsearch/v7/esapi
    
    the code of the file until where you have to start completion: // Licensed to Elasticsearch B.V under one or more agreements.
// Elasticsearch B.V. licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information.
//
// Code generated from specification version 7.12.0: DO NOT EDIT

package esapi

import (
	"context"
	"io"
	"net/http"
	"strconv"
	"strings"
)

func newExplainFunc(t Transport) Explain {
	return func(index string, id string, o ...func(*ExplainRequest)) (*Response, error) {
		var r = ExplainRequest{Index: index, DocumentID: id}
		for _, f := range o {
			f(&r)
		}
		return r.Do(r.ctx, t)
	}
}

// ----- API Definition -------------------------------------------------------

// Explain returns information about why a specific matches (or doesn't match) a query.
//
// See full documentation at https://www.elastic.co/guide/en/elasticsearch/reference/master/search-explain.html.
//
type Explain func(index string, id string, o ...func(*ExplainRequest)) (*Response, error)

// ExplainRequest configures the Explain API request.
//
type ExplainRequest struct {
	Index        string
	DocumentType string
	DocumentID   string

	Body io.Reader

	Analyzer        string
	AnalyzeWildcard *bool
	DefaultOperator string
	Df              string
	Lenient         *bool
	Preference      string
	Query           string
	Routing         string
	Source          []string
	SourceExcludes  []string
	SourceIncludes  []string
	StoredFields    []string

	Pretty     bool
	Human      bool
	ErrorTrace bool
	FilterPath []string

	Header http.Header

	ctx context.Context
}

// Do executes the request and returns response or error.
//
func (r ExplainRequest) Do(ctx context.Context, transport Transport) (*Response, error) {
	var (
		method string
		path   strings.Builder
		params map[string]string
	)

	method = "GET"

	if r.DocumentType == "" {
		r.DocumentType = "_doc"
	}

	path.Grow(1 + 
    
func (r ExplainRequest) Do(ctx context.Context, transport Transport) (*Response, error) {
	var (
		method string
		path   strings.Builder
		params map[string]string
	)

	method = "GET"

	if r.DocumentType == "" {
		r.DocumentType = "_doc"
	}

	path.Grow(1 + len(r.Index) + 1 + len(r.DocumentType) + 1 + len(r.DocumentID) + 1 + len("_explain"))
	path.WriteString("/")
	path.WriteString(r.Index)
	if r.DocumentType != "" {
		path.WriteString("/")
		path.WriteString(r.DocumentType)
	}
	path.WriteString("/")
	path.WriteString(r.DocumentID)
	path.WriteString("/")
	path.WriteString("_explain")

	params = make(map[string]string)

	if r.Analyzer != "" {
		params["analyzer"] = r.Analyzer
	}

	if r.AnalyzeWildcard != nil {
		params["analyze_wildcard"] = strconv.FormatBool(*r.AnalyzeWildcard)
	}

	if r.DefaultOperator != "" {
		params["default_operator"] = r.DefaultOperator
	}

	if r.Df != "" {
		params["df"] = r.Df
	}

	if r.Lenient != nil {
		params["lenient"] = strconv.FormatBool(*r.Lenient)
	}

	if r.Preference != "" {
		params["preference"] = r.Preference
	}

	if r.Query != "" {
		params["q"] = r.Query
	}

	if r.Routing != "" {
		params["routing"] = r.Routing
	}

	if len(r.Source) > 0 {
		params["_source"] = strings.Join(r.Source, ",")
	}

	if len(r.SourceExcludes) > 0 {
		params["_source_excludes"] = strings.Join(r.SourceExcludes, ",")
	}

	if len(r.SourceIncludes) > 0 {
		params["_source_includes"] = strings.Join(r.SourceIncludes, ",")
	}

	if len(r.StoredFields) > 0 {
		params["stored_fields"] = strings.Join(r.StoredFields, ",")
	}

	if r.Pretty {
		params["pretty"] = "true"
	}

	if r.Human {
		params["human"] = "true"
	}

	if r.ErrorTrace {
		params["error_trace"] = "true"
	}

	if len(r.FilterPath) > 0 {
		params["filter_path"] = strings.Join(r.FilterPath, ",")
	}

	req, err := newRequest(method, path.String(), r.Body)
	if err != nil {
		return nil, err
	}

	if len(params) > 0 {
		q := req.URL.Query()
		for k, v := range params {
			q.Set(k, v)
		}
		req.URL.RawQuery = q.Encode()
	}

	if r.Body != nil {
		req.Header[headerContentType] = headerContentTypeJSON
	}

	if len(r.Header) > 0 {
		if len(req.Header) == 0 {
			req.Header = r.Header
		} else {
			for k, vv := range r.Header {
				for _, v := range vv {
					req.Header.Add(k, v)
				}
			}
		}
	}

	if ctx != nil {
		req = req.WithContext(ctx)
	}

	res, err := transport.Perform(req)
	if err != nil {
		return nil, err
	}

	response := Response{
		StatusCode: res.StatusCode,
		Body:       res.Body,
		Header:     res.Header,
	}

	return &response, nil
}