<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def txn_storeAssociation(self, server_url, association):
 """Set the association for the server URL. Association -> NoneType """

        a = association
        self.db_set_assoc(
            server_url,
            a.handle,
            self.blobEncode(a.secret),
            a.issued,
            a.lifetime,
            a.assoc_type)