regions property Null safety
Show rectangles inside the chart. This option accepts array including object that has axis, start, end and class. The keys start, end and class are optional. axis must be x, y or y2. start and end should be the value where regions start and end. If not specified, the edge values will be used. If timeseries x axis, date string, Date object and unixtime integer can be used. If class is set, the region element will have it as class.
external List<RegionOptions> get regions;
external set regions(List<RegionOptions> v);