<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def fetch(self, endpoint, data = None):
 """ for getting data after logged in """

        payload = {
            "lastServerChangeId": "-1",
            "csrf": self.__csrf,
            "apiClient": "WEB"
        }
        if data is not None:
            payload.update(data)

        return self.post(endpoint, payload)