@abc.abstractmethod<EOL><INDENT>def get_configurations(self):<DEDENT>
return<EOL>
Gets all ``Configurations,`` In plenary mode, the returned list contains all known configurations or an error
        results.

        Otherwise, the returned list may contain only those
        configurations that are accessible through this session.

        :return: a list of ``Configurations``
        :rtype: ``osid.configuration.ConfigurationList``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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