Also, I noticed in the documentation for `csv.DictWriter` (https://docs.python.org/3/library/csv.html#csv.DictWriter.writeheader) does not contain the following line -
     to the writer's file object, formatted according to the current dialect.
Although it is there for the other 2 methods (`writerow` & `writerows`) and since `writeheader` uses `writerow` in turn, I believe the said line should be included for the `writeheader` documentation as well. I have created another patch with both the changes. I ran the Doc build (make html) and have checked the addition of the said lines looks good & does not break anything.

I can make another thread if required, if you feel both the changes can't be accommodated in the same issue.