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In the documentation, I noticed several uses of ``.. versionchanged::`` that described things which had been added. 
I love Python, and its documentation, and I wanted to contribute. So, I figured a low-risk contribution would be to change ``.. versionchanged::`` to ".. versionadded" where appropriate. (I also tweaked the descriptions accordingly. E.g., "Added the *x* argument" became "The *x* argument", because it’s unnecessary to say "added" in a description under ".. versionadded".)
I did also make a few unrelated tweaks along the way--all very minor, and related to phrasing or formatting. 
Please let me know if I can do anything else to get this merged!