Gradient Fill does not work properly in some charts
(1)Chart plot area
The degree(direction of gradation) parameter cannot be changed from default value(=0).
For example, following does not work.
gfProp = GradientFillProperties()
gfProp.degree = 90
In the case of 'cell' parameters, it seems no problem.
The default degree = 0, and it cannot be changed.
(2)Border area of chart
Any parameter of 'Fill' does not work in this case.
If 'cs.spPr = self.graphical_properties' is added, in def _write(self) of _chart.py,
it works. However, 'degree' parameter as mentioned above is also neglected.
An example of 'chart.graphical_properties = GraphicalProperties(noFill=True)' is following.