Returns the dimensions corresponding to each axis.

        Should return a list of dimensions or list of lists of
        dimensions, which will be formatted to label the axis
        and to link axes.

def _get_axis_dims(self, element):
        """Returns the dimensions corresponding to each axis.

        Should return a list of dimensions or list of lists of
        dimensions, which will be formatted to label the axis
        and to link axes.
        """
        dims = element.dimensions()[:2]
        if len(dims) == 1:
            return dims + [None, None]
        else:
            return dims + [None]