https://pandas.pydata.org/pandas-docs/stable/indexing.html
https://pandas.pydata.org/pandas-docs/stable/advanced.html
https://www.datacamp.com/community/tutorials/pandas-multi-index
https://pandas.pydata.org/pandas-docs/stable/cookbook.html#cookbook-multi-index

https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Index.html
    https://pandas.pydata.org/pandas-docs/stable/visualization.html#subplots

df.sort_index(
    by='column_name',
    inplace=True,
)

df
    .index
    .unstack().index


dfr = pd.DataFrame(df.unstack())

droplevel
dfr.columns = dfr.columns.droplevel(0)