@abc.abstractmethod<EOL><INDENT>def skip(self, n):<DEDENT>
return<EOL>
Skips a specified number of ``bytes`` in the stream.

        :param n: the number of ``bytes`` to skip
        :type n: ``cardinal``
        :return: the actual number of ``bytes`` skipped
        :rtype: ``cardinal``
        :raise: ``IllegalState`` -- this stream has been closed or ``at_end_of_stream()`` is ``true``

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