GMSPolygonLayer
@interface GMSPolygonLayer : GMSOverlayLayerGMSPolygonLayer is a subclass of GMSOverlayLayer, available on a per-polygon basis, that
 allows animation of several properties of its associated GMSPolygon.
Note that this CALayer is never actually rendered directly, as GMSMapView is provided
 entirely via an OpenGL layer. As such, adjustments or animations to ‘default’ properties of
 CALayer will not have any effect.
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                  The width of the polygon outline in screen points. DeclarationSwift var strokeWidth: CGFloat { get set }Objective-C @property (nonatomic) CGFloat strokeWidth;
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                  The color of the polygon outline. This is an assign property, there is an expectation for the GMSPolygonto own the reference if necessary.DeclarationSwift unowned(unsafe) var strokeColor: CGColor? { get set }Objective-C @property (nonatomic, nullable) CGColorRef strokeColor;
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                  The fill color. This is an assign property, there is an expectation for the GMSPolygonto own the reference if necessary.DeclarationSwift unowned(unsafe) var fillColor: CGColor? { get set }Objective-C @property (nonatomic, nullable) CGColorRef fillColor;