def _get_size(self):
return <NUM_LIT:0><EOL>
I{(subclass override)}
Return the size of the file.  This is called from within L{_set_mode}
if the file is opened in append mode, so the file position can be
tracked and L{seek} and L{tell} will work correctly.  If the file is
a stream that can't be randomly accessed, you don't need to override
this method,