Support more DataFrame methods

[seeM]

Here is a full list of outstanding DataFrame methods we'd like to eventually support. Each of these should be added in a separate PR. I'd recommend looking to tidylog for inspiration of actual implementation and log message content.

Select columns and/or filter rows

• df.loc, df.iloc
  • note that these are properties, which won't work exactly the same as others
  • could also just re-order columns

Adding columns

• df.assign
• df.__setitem__
• df.loc, df.iloc
  • how to handle this being used for both getting and setting?

Indexes

• df.reindex

Joining

• df.merge
• df.join
• df.concat
• pd.merge
• pd.merge_asof

Reshaping

• df.stack
• df.unstack

Aggregating

• df.pivot_table
• df.groupby

Misc

• df.pipe?