code: func (r *BulkIndexRequest) VersionType(versionType string) *BulkIndexRequest {
  	r.versionType = versionType
  	r.source = nil
  	return r
  }
docs: // VersionType specifies how versions are created. It can be e.g. internal,
  // external, external_gte, or force.
  //
  // See https://www.elastic.co/guide/en/elasticsearch/reference/7.0/docs-index_.html#index-versioning
  // for details.