Release 3.5.2

Fixed

• Fix type annotations for convertFile - it accepts only bytes-based buffers.
  Also remove legacy checks from Python 2 (#1400)
• Remove legacy import needed only in Python 2 (#1403)
• Fix typo that left the attribute AdmonitionProcessor.content_indent unset
  (#1404)
• Fix edge-case crash in InlineProcessor with AtomicString (#1406).
• Fix edge-case crash in codehilite with an empty code tag (#1405).
• Improve and expand type annotations in the code base (#1401).
• Fix handling of bogus comments (#1425).