code: function CompositeFilter(properties) {
                          this.filters = [];
                          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 CompositeFilter.
  @memberof google.firestore.v1.StructuredQuery
  @interface ICompositeFilter
  @property {google.firestore.v1.StructuredQuery.CompositeFilter.Operator|null} [op] CompositeFilter op
  @property {Array.<google.firestore.v1.StructuredQuery.IFilter>|null} [filters] CompositeFilter filters
   
  Constructs a new CompositeFilter.
  @memberof google.firestore.v1.StructuredQuery
  @classdesc Represents a CompositeFilter.
  @implements ICompositeFilter
  @constructor
  @param {google.firestore.v1.StructuredQuery.ICompositeFilter=} [properties] Properties to set