in <code>common_pt_inputs</code>), and inputs that are unique to
that patient and that treatment (<code>unique_pt_inputs</code>). Items
can be included through the <code>add_item</code> function, and can be
used in subsequent items. All these inputs are generated before the
events and the reaction to events are executed. Furthermore, the program
first executes <code>common_all_inputs</code>, then
<code>common_pt_inputs</code> and then <code>unique_pt_inputs</code>. So
one could use the items generated in <c