implementation to generate a design
matrix of spline basis functions of covariates and interactions of
covariates. The lasso regression is fit to this design matrix via
<code><a href="https://glmnet.stanford.edu/reference/cv.glmnet.html" class="external-link">cv.glmnet</a></code> or a custom implementation derived from
<span class="pkg">origami</span>. The maximum dimension of the design matrix is \(n\) -by-
\((n * 2^(d-1))\), where where \(n\) is the number of observations and
\(d\) is the number of covari