graphical_properties of PieChart doesn't work
*Created originally on Bitbucket by [liuyuqian](https://bitbucket.org/%7B987af662-7ddf-415a-b86c-03da3f6cb95f%7D/)*
I tried to add solidFill、pattFill、noFill to the background of piechart,refer to this mail:
https://groups.google.com/forum/#!searchin/openpyxl-users/graphicalProperties|sort:relevance/openpyxl-users/ZOQByC-rKJI/BnS3UydCAwAJ
I made several tries,but none of them works,it seems that graphical_properties of PieChart doesn't work,unlike graphical_properties of series.
# --------- 1 -------------
```
#!python
props = GraphicalProperties(solidFill="CC0000")
pie.graphical_properties = props
pie.plot_area.graphical_properites = props
pie.graphicalProperties = props
pie.plot_area.graphicalProperties = props
```
# --------- 2 -------------
```
#!python
pie.graphicalProperties = GraphicalProperties(solidFill= drawing.colors.ColorChoice(prstClr='blue'))
pie.plot_area.graphicalProperties = GraphicalProperties(solidFill= drawing.colors.ColorChoice(prstClr='red'))
pie.graphical_properties = GraphicalProperties(solidFill= drawing.colors.ColorChoice(prstClr='blue'))
pie.plot_area.graphical_properties = GraphicalProperties(solidFill= drawing.colors.ColorChoice(prstClr='red'))
```
# --------- 3 -------------
```
#!python
fill = PatternFillProperties(prst="pct5")
fill.foreground = ColorChoice(prstClr="red")
fill.background = ColorChoice(prstClr="blue")
pie.graphicalProperties.pattFill=fill
pie.plot_area.graphicalProperties.pattFill=fill
pie.graphical_properties.pattFill=fill
pie.plot_area.graphical_properties.pattFill=fill
```
Thanks~
*Attachments:* [pie.py](/uploads/668e01ca894438acc2c0f73dfe67ca59/pie.py)[pie.xlsx](/uploads/f5c71c7699b97a1c042d907e1e64fc12/pie.xlsx)
issue