Demonstration of bug in mongokit custom type handling

testcase.py

import datetime
from mongokit import CustomType, Document, Connection

class CustomDate(CustomType):
    mongo_type = unicode
    python_type = datetime.datetime # optional, just for more validation
    init_type = None # optional, fill the first empty value

    def to_bson(self, value):
        """convert type to a mongodb type"""
        return unicode(datetime.datetime.strftime(value,'%y-%m-%d'))

    def to_python(self, value):
        """convert type to a python object"""
        if value is not None:
            return datetime.datetime.strptime(value, '%y-%m-%d')

    def validate(self, value, path):
        """OPTIONAL : useful to add a validation layer"""
        if value is not None:
            pass #  do something here

class MyDoc(Document):
    structure = {
        'dates': {unicode: CustomDate()}
    }

conn = Connection('localhost')
conn.register([MyDoc])
doc = conn.test.docs.MyDoc()
doc[u'dates'][u'birthdate'] = datetime.datetime(2003,2,1)
doc.validate()