PX doesn't force category orders on axes

[nicolaskruchten]

This causes ordering issues like this:

import plotly.express as px
import pandas as pd

df = pd.DataFrame(dict(
    x=['a','b','c','d'],
    y=[1,2,3,4],
    z=['p','q','p','q']
))

px.bar(df, x="x", y="y", color="z")

[nicolaskruchten]

The workaround right now is to do category_orders=dict(x=df.z.unique()) but ideally this would be done internally.