DOC: Use of "Yields" vs "Returns" for documentation of DataFrame.items() and DataFrame.iteritems() 
`DataFrame.items()` says it "Yields" the label and content of the columns whereas `DataFrame.iteritems()` says it "Returns" the label and content of the columns

https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.items.html
https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.iteritems.html