code: function ListDocumentsRequest(properties) {
                      if (properties)
                          for (var keys = Object.keys(properties), i = 0; i < keys.length; ++i)
                              if (properties[keys[i]] != null)
                                  this[keys[i]] = properties[keys[i]];
                  }
docs: Properties of a ListDocumentsRequest.
  @memberof google.firestore.v1
  @interface IListDocumentsRequest
  @property {string|null} [parent] ListDocumentsRequest parent
  @property {string|null} [collectionId] ListDocumentsRequest collectionId
  @property {number|null} [pageSize] ListDocumentsRequest pageSize
  @property {string|null} [pageToken] ListDocumentsRequest pageToken
  @property {string|null} [orderBy] ListDocumentsRequest orderBy
  @property {google.firestore.v1.IDocumentMask|null} [mask] ListDocumentsRequest mask
  @property {Uint8Array|null} [transaction] ListDocumentsRequest transaction
  @property {google.protobuf.ITimestamp|null} [readTime] ListDocumentsRequest readTime
  @property {boolean|null} [showMissing] ListDocumentsRequest showMissing
   
  Constructs a new ListDocumentsRequest.
  @memberof google.firestore.v1
  @classdesc Represents a ListDocumentsRequest.
  @implements IListDocumentsRequest
  @constructor
  @param {google.firestore.v1.IListDocumentsRequest=} [properties] Properties to set