"L_term"."L_term" object represents the linear term of the "L_constraint".
Objects from the following classes can be coerced to "L_term":
"NULL", "numeric", "matrix", "simple_triplet_matrix"
and "list".
as.L_term(x, ...)"simple_triplet_zero_matrix"
lists "as.Q_term" is applied to every element
of the list, for NULL one can supply the optional arguments "nrow"
and "ncol" which will create a "simple_triplet_zero_matrix"
with the specified dimension.