The protocol which class providing data that is changed in runtime should conforms.
@protocol DXChangeableSeriesData <NSObject>
A class adopting the protocol should notify its delegate about data changes to update data representation.
The optional property. Returns the delegate of a series data.
@property (nonatomic, weak) id<DXSeriesDataDelegate> delegate
An instance of a class adopting the DXSeriesDataDelegate protocol, that is the delegate of the series data.
A data class should notify this delegate about data changes to update a visual representation of the data.