tileMode property Null safety
Gradient tiles in the plane beyond the region before its
starting stop and after its ending stop.
For details, see TileMode.
TileMode get tileMode => (this is IntermediateGradient) ? (this as IntermediateGradient).packet.tileMode : (this is LinearGradient) ? (this as LinearGradient).tileMode : (this is RadialGradient) ? (this as RadialGradient).tileMode : (this is SweepGradient) ? (this as SweepGradient).tileMode : (this is Steps) ? (this as Steps).tileMode : TileMode.clamp;