Thanks to the feedback in the Discourse thread, we will be changing the signature such that a tag function will be passed an object implementing a Template prot

Thanks to the feedback in the Discourse thread, we will be changing the signature such that a tag function will be passed an object implementing a Template protocol, with attributes source, for the original source string as written; and attribute args for what was *args in the starting version of the PEP. Template.source can act as a memoization key.