cifying the maximum number of knot points (i.e., bins) for any covariate
for generating basis functions. If <code>num_knots</code> is a unit-length
vector, then the same <code>num_knots</code> are used for each degree (this is
not recommended). The default settings for <code>num_knots</code> are
recommended, and these defaults decrease <code>num_knots</code> with increasing
<code>max_degree</code> and <code>smoothness_orders</code>, which prevents (expensive)
combinatorial explosions in the number of higher