How i'd parse display_hints

display_hints.py

#!/usr/bin/env python

# see https://docs.google.com/document/d/1m4VTRqclB3JEMZBjbr4t5cvIMQUNSGxy6rYN4YtopIk/edit#heading=h.92ptkhvsmxtd

def recognised(type):
    # a smart client who understands indexed types will strip off any indexing:
    # import re
    # type = re.sub(r'\.\d+$', '', type)

    # a typical smart client:
    return type in ["m.calendar.request", "m.location", "m.file", "m.thumbnail", "m.html", "m.text"]    

    # or a typical dumb client:
    # return type in ["m.file", "m.thumbnail", "m.html", "m.text"]

    # or a very dumb client
    # return type in ["m.text"]

def parse_display_hints(display_hints):
    for hint in display_hints:
        display_types = {}
        target_type_count = len(hint)
        for term in hint:
            if type(term) is str and recognised(term):
                display_types[term] = True
            elif type(term) is list:
                for option in term:
                    if option is None:
                        target_type_count -= 1
                    elif recognised(option):
                        display_types[option] = True
                        break
        if len(display_types) == target_type_count:
            return display_types

display_hints = [
    [ "m.calendar.request", [ "m.location", None ], "m.file" ],
    [ "m.file", [ "m.thumbnail.1", "m.thumbnail", None ], [ "m.html", "m.markdown", "m.text" ] ],
    [ "m.html" ], # implicit
    [ "m.text" ], # implicit    
]

print parse_display_hints(display_hints).keys()