toJson method
Implementation
core.Map<core.String, core.dynamic> toJson() => {
if (heightPx != null) 'heightPx': heightPx!,
if (leftPx != null) 'leftPx': leftPx!,
if (topPx != null) 'topPx': topPx!,
if (widthPx != null) 'widthPx': widthPx!,
};