gasman

import re
from hashlib import md5

def gfm(text):
    # Extract pre blocks.
    extractions = {}
    def pre_extraction_callback(matchobj):
        digest = md5(matchobj.group(0).encode('utf-8')).hexdigest()
        extractions[digest] = matchobj.group(0)
        return "{gfm-extraction-%s}" % digest