validates the given data against this object's rules and then
        updates

def update(self, **kwargs):
        ''' validates the given data against this object's rules and then
        updates '''
        redis = type(self).get_redis()
        errors = ValidationErrors()

        for fieldname, field in self.proxy:
            if not field.fillable:
                continue

            given = kwargs.get(fieldname)

            if given is None:
                continue

            try:
                value = field.validate(kwargs.get(fieldname), redis)
            except BadField as e:
                errors.append(e)
                continue

            setattr(
                self,
                fieldname,
                value
            )

        if errors.has_errors():
            raise errors

        return self.save()