@abc.abstractmethod<EOL><INDENT>def update_bank(self, bank_form):<DEDENT>
pass<EOL>
Updates an existing bank.

        :param bank_form: the form containing the elements to be updated
        :type bank_form: ``osid.assessment.BankForm``
        :raise: ``IllegalState`` -- ``bank_form`` already used in an update transaction
        :raise: ``InvalidArgument`` -- the form contains an invalid value
        :raise: ``NullArgument`` -- ``bank_form`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure occurred
        :raise: ``Unsupported`` -- ``bank_form`` did not originate from ``get_bank_form_for_update()``

        *compliance: mandatory -- This method must be implemented.*