def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def step_impl(context):
    data = json.loads(context.text)
    receiver_name = re.match(r"\<(\w+)'s id\>", data['receiver']).group(1)
    data['receiver'] = context.users[receiver_name]['id']
    context.request.add_data(data)