Priority is a pure-Python implementation of the priority logic for HTTP/2, set
out in RFC 7540 Section 5.3 (Stream Priority). This logic allows for clients to
express a preference for how the server allocates its (limited) resources to the
many outstanding HTTP requests that may be running over a single HTTP/2
connection.

Specifically, this Python implementation uses a variant of the implementation
used in the excellent H2O project. This original implementation is also the
inspiration for nghttp2's priority implementation, and generally produces a very
clean and even priority stream. The only notable changes from H2O's
implementation are small modifications to allow the priority implementation to
work cleanly as a separate implementation, rather than being embedded in a
HTTP/2 stack directly.

While priority information in HTTP/2 is only a suggestion, rather than an
enforceable constraint, where possible servers should respect the priority
requests of their clients.