ModelChoiceField for mongoengine

gistfile1.txt

class MongoModelChoiceField(ModelChoiceField):
# this works if you pass the field a queryset keyword argument. I doubt it works with a model as the argument
# does not support to_field_name, but that would be easy
    def to_python(self, value):
        if value in EMPTY_VALUES:
            return None
        # mongoengine has no deepcopy as yet, so we can't do:
        #   querycopy = self.queryset.copy()
        #   value = querycopy.filter(pk=value.pk).first()
        # instead:
        for x in self.queryset:
            if str(x.id) == str(value):
                return x
        return None