- fix imports
- pep8
- The :meth:`.Query.update` method will now convert string key
names in the given dictionary of values into mapped attribute names
against the mapped class being updated.  Previously, string names
were taken in directly and passed to the core update statement without
any means to resolve against the mapped entity.  Support for synonyms
and hybrid attributes as the subject attributes of
:meth:`.Query.update` are also supported.
fixes #3228