def save(self, filename):
self.export(filename, file_format="<STR_LIT>")<EOL>
Save a grid object to <filename>.pickle

        Internally, this calls
        ``Grid.export(filename, format="python")``. A grid can be
        regenerated from the saved data with ::

           g = Grid(filename="grid.pickle")

        .. note::
           The pickle format depends on the Python version and
           therefore it is not guaranteed that a grid saved with, say,
           Python 2.7 can also be read with Python 3.5. The OpenDX format
           is a better alternative for portability.