Is your feature request related to a problem?

Adding inplace argument for df.join() will be more in line with Pandas environment.

Describe the solution you'd like

Add an inplace parameter in df.join() so that it becomes
df.join(obj,.... inplace=False)

API breaking implications

None

Describe alternatives you've considered

Alternative is to assign the new df in place of old df by doing
df = df.join(other_df)