ModelCustom's S3 predict method is not working

[asiripanich]

ModelBinaryChoice, ModelMultinomialLogit, ModelLinear still need a little more work.

• If the LHS of the formula is missing from newdata then the predict method won't work. This can be fixed by omitting the LHS variable in model.matrix which is possible with the Formula package.

form <- Formula::Formula(sex ~ age + marital_status)
mm <- model.matrix(form, toy_individuals, lhs = 0)