@abc.abstractmethod<EOL><INDENT>def set_completion(self, completion):<DEDENT>
pass<EOL>
Sets the completion percentage.

        :param completion: the completion percentage
        :type completion: ``decimal``
        :raise: ``InvalidArgument`` -- ``completion`` is invalid
        :raise: ``NoAccess`` -- ``Metadata.isReadOnly()`` is ``true``

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