Turns all gridlines on or off

        :param bool grid: turns the gridlines on if ``True``, off if ``False``

def grid(self, grid):
        """Turns all gridlines on or off

        :param bool grid: turns the gridlines on if ``True``, off if ``False``"""

        if not isinstance(grid, bool):
            raise TypeError("grid must be boolean, not '%s'" % grid)
        self._x_grid = self._y_grid = grid