Create formulas from the utility functions such that we can create correct
model matrices.

## Arguments

- x
An object of class utility

## Value

A list of formula expressions for the utility functions

## Details

Note that this function should be used on a cleaned utility expression and
**not** an updated utility expression. This is because we are converting
dummy coded attributes to factors prior to calling `model.matrix`

.
This ensures that dummy coded attributes are correctly returned with the
model matrix.