Insert containers laid out as side-by-side columns.
Inserts a number of multi-element containers laid out side-by-side and returns a list of container objects.
To add elements to the returned containers, you can use "with" notation (preferred) or just call methods directly on the returned object. See examples below.
Currently, you may not put columns inside another column.
spec (int or list of numbers)
(list of containers)
A list of container objects.