@abc.abstractmethod<EOL><INDENT>def change_branch(self, branch_id, proxy):<DEDENT>
pass<EOL>
Changes the service branch.

        :param branch_id: the new service branch
        :type branch_id: ``osid.id.Id``
        :param proxy: a proxy
        :type proxy: ``osid.proxy.Proxy``
        :raise: ``NotFound`` -- ``branch_id`` not found
        :raise: ``NullArgument`` -- ``branch_id`` or ``proxy`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure occurred
        :raise: ``Unimplemented`` -- ``supports_journal_branching()`` is ``false``

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