'Plot gridlines for both coordinates.
Standard matplotlib appearance options (color, alpha, etc.) can be
passed as keyword arguments.
Parameters
draw_grid : bool
Whether to show the gridlines
grid_type : { \'lines\' | \'contours\' }
Whether to plot the contours by determining the grid lines in
world coordinates and then plotting them in world coordinates
(``\'lines\'``) or by determining the world coordinates at many
positions in the image and then drawing contours
(``\'contours\'``). The first is recommended for 2-d images, while
for 3-d (or higher dimensional) cubes, the ``\'contours\'`` option
is recommended.'

def grid(self, draw_grid=True, grid_type='lines', **kwargs):

    for coord in self:
        coord.grid(draw_grid=draw_grid, grid_type=grid_type, **kwargs)
