What is the preferred MASTER_SITES for python port?

[Sergey Akhmatov]

Hello.

Suppose I want to port some python package that exists in the Python 
Package Index (PyPI) and has it's source code available on some official 
website or github.

Is there any policy or recommended practice for choosing MASTER_SITES? 
Should I use "USE_GITHUB=yes" or "MASTER_SITES= CHEESESHOP" for such 
package?

I've looked for the answer in Porters Handbook and at 
https://wiki.freebsd.org/Python/PortsPolicy but haven't found it.

Thank you.