The functions to add/modify events/inputs use lists. Whenever several inputs/events are added or modified, it's recommended to group them within one function, as it reduces the computation cost.
So rather than use two modify_item with a list of one element, it's better to group them into a single modify_item with a list of two elements.
Costs and utilities can be modified by using the construction type_name_category, where type is either "qaly" or "cost",
name is the name (e.g., "default") and category is the category used (e.g., "instant"), so one could pass cost_default_instant and modify the cost.
This will overwrite the value defined in the corresponding cost/utility section.
The function is different from modify_item in that this function evaluates sequentially the arguments within the list passed.
This implies a slower performance relative to modify_item, but it can be more cleaner and convenient in certain instances.
This function is intended to be used only within the add_reactevt function in its input parameter and should not be run elsewhere or it will return an error.