,[2]]: indicates different choices for data, x and y.</p>
<p>In this context, special values can be used to indicate different type of defaults (N.B.: vars are in order matching <cite>data, x, y</cite>), these are internally converted to the proper format:
None: don’t include element (e.g. [1,2] is equivalent to [[1,2],None,None])
[]:  use default (e.g. [[0,2],[],None] uses default for x and doesn’t report y)
[[]]: use full set of variables (e.g. [[0,2],[],[[]]] uses default for x and full stats for y, 