Improving performance in Python 2.7

A lot of the motivation for the type hints work has been to consolidate the existing type inference stuff that's being done independently by PyCharm, Google's internal linting tools, Microsoft's Visual-Studio-for-Python, etc. So what's new in 3.5 isn't so much the existence of type inference, but that now there's a standard way for these different projects to collaborate with each other and with third-party libraries using a common language.