GMSURLTileLayer
@interface GMSURLTileLayer : GMSTileLayerGMSURLTileProvider fetches tiles based on the URLs returned from a GMSTileURLConstructor. For
 example:
 
   GMSTileURLConstructor constructor = ^(NSUInteger x, NSUInteger y, NSUInteger zoom) {
     NSString *URLStr =
         [NSString stringWithFormat:@"https://example.com/%d/%d/%d.png", x, y, zoom];
     return [NSURL URLWithString:URLStr];
   };
   GMSTileLayer *layer =
       [GMSURLTileLayer tileLayerWithURLConstructor:constructor];
   layer.userAgent = @"SDK user agent";
   layer.map = map;
 GMSURLTileProvider may not be subclassed and should only be created via its convenience
 constructor.
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                  Convenience constructor. constructormust be non-nil.DeclarationSwift convenience init(urlConstructor constructor: @escaping GMSTileURLConstructor)Objective-C + (nonnull instancetype)tileLayerWithURLConstructor: (nonnull GMSTileURLConstructor)constructor;
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                  Specify the user agent to describe your application. If this is nil (the default), the default iOS user agent is used for HTTP requests. DeclarationSwift var userAgent: String? { get set }Objective-C @property (nonatomic, copy, nullable) NSString *userAgent;