Clean's up a nested structure for mongo

mongocleanup.py

import re

def mongo_cleanup(item, replacement=''):
    """clean's a nested structure keys to adapt to mongodb's
    legal keys
    see http://www.mongodb.org/display/DOCS/Legal+Key+Names """
    if hasattr(item, 'items'):
        newdict = {}
        for key, value in item.items():
            nkey = key
            if isinstance(key, basestring):
                # nkey = re.sub('(^\$)|\.', replacement, key)
                nkey = re.sub('\.', replacement, key)
                nkey = re.sub('(^\$)', "dollar_", nkey)
                nkey = nkey.replace('\x00', '')

            newdict[nkey] = mongo_cleanup(value, replacement)
        return newdict
    elif isinstance(item, list):
        return [mongo_cleanup(val, replacement) for val in item]
    else:
        return item