added metadata to choropleth.py (#11984)
added metadata to choropleth.py (#11984)

* added metadata to choropleth.py

* Update examples/plotting/file/choropleth.py

Co-authored-by: Bryan Van de Ven <0a3ba1af216659500dd8f41e29f3979f42452870@bokeh.org>

Co-authored-by: Bryan Van de Ven <0a3ba1af216659500dd8f41e29f3979f42452870@bokeh.org>
bokeh/bokeh,bokeh/bokeh,bokeh/bokeh,bokeh/bokeh,bokeh/bokeh