Log Message:
py-singledispatch: updated to 3.6.2

v3.6.2
Fix behavior when metaclass implements bool.

v3.6.1
Fixed DeprecationWarnings referring to members from
``collections.abc`` referenced from ``collections``.

v3.6.0
Added support for annotations as found on Python 3.7.

v3.5.0
Adopt semver for versioning.
Adopt jaraco/skeleton for packaging.
Declare support through 3.9.
Tests now pass under pytest and when typing is present.