Deletes unused grid row/cols

def remove_unused_grid_rc(self):
        """Deletes unused grid row/cols"""

        if 'columns' in self['layout']:
            ckeys = tuple(self['layout']['columns'].keys())
            for key in ckeys:
                value = int(key)
                if value > self.max_col:
                    del self['layout']['columns'][key]
        if 'rows' in self['layout']:
            rkeys = tuple(self['layout']['rows'].keys())
            for key in rkeys:
                value = int(key)
                if value > self.max_row:
                    del self['layout']['rows'][key]