@abc.abstractmethod<EOL><INDENT>def get_authentication(self):<DEDENT>
return<EOL>
Gets the authentication credential for the current user.

        The input data may represent the identity of the remote peer or
        data from a challenge-response transaction necessary for
        generating the credantial.

        :return: the acquired authentication credential
        :rtype: ``osid.authentication.process.Authentication``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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