Dart APIunself_componentUnSliverArtBardescription description property Null safety Widget? description final Implementation final Widget? description; unself_component unself_component UnSliverArtBar description property UnSliverArtBar class Constructors UnSliverArtBar Properties action background description emoji hashCode isImmersive key leading name runtimeType trailing Methods createElement createState debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator ==