A generator that creates labels for the series in an
XYDataset .
Classes that implement this interface should be either (a) immutable, or
(b) cloneable via the PublicCloneable interface (defined in
the JCommon class library). This provides a mechanism for the referring
renderer to clone the generator if necessary.
Generates a label for the specified series. This label will be
used for the chart legend.
Parameters: dataset - the dataset (null not permitted). Parameters: series - the series. A series label.