PEP 3118 Buffer Protocol Support for Series
Just a POC and not sure we want this but was curious nonetheless...

This extension module allows a Series to conform to the buffer protocol, which makes it readable / writeable through memoryviews. Right now in places like groupby we always in user code extract out the underlying array and pass that through Cython, which this in theory could centralize while helping third party code that may use this as well

Getting this to work with a DataFrame would be the bigger win but also takes more effort, so leaving that for another day