code: def skip(self, n):
          
          if self._my_data.closed or self.at_end_of_stream():
              raise IllegalState()
          if n is not None:
              self._my_data.seek(n)
docs: Skips a specified number of ``bytes`` in the stream.
  
          arg:    n (cardinal): the number of ``bytes`` to skip
          return: (cardinal) - the actual number of ``bytes`` skipped
          raise:  IllegalState - this stream has been closed or
                  ``at_end_of_stream()`` is ``true``
          *compliance: mandatory -- This method must be implemented.*