Doc upgrade checklist:

-[ ] old boilerplate at top and bottom of file has been removed

-[ ] Every example is independently runnable and is optimized for short line count

-[ ] no more`plot()` or`iplot()`

-[ ]`graph_objs` has been renamed to`graph_objects`

-[ ]`fig = <something>` call is high up in each example

-[ ] minimal creation of intermediate`trace` objects

-[ ] liberal use of`add_trace` and`update_layout`

-[ ]`fig.show()` at the end of each example

-[ ]`px` example at the top if appropriate

-[ ]`v4upgrade: true` metadata added

-[ ] minimize usage of hex codes for colors in favour of those inhttps://github.com/plotly/plotly.py-docs/issues/14