code: function DocumentTransform(properties) {
                      this.fieldTransforms = [];
                      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 DocumentTransform.
  @memberof google.firestore.v1
  @interface IDocumentTransform
  @property {string|null} [document] DocumentTransform document
  @property {Array.<google.firestore.v1.DocumentTransform.IFieldTransform>|null} [fieldTransforms] DocumentTransform fieldTransforms
   
  Constructs a new DocumentTransform.
  @memberof google.firestore.v1
  @classdesc Represents a DocumentTransform.
  @implements IDocumentTransform
  @constructor
  @param {google.firestore.v1.IDocumentTransform=} [properties] Properties to set