model: Model statement for competing event variable.
compevent_restrictions: List of vectors. Each vector containins as its first entry a condition and its second entry an integer. When the condition is TRUE, the competing event variable is simulated according to the fitted model; when the condition is FALSE, the competing event variable takes on the value in the second entry.
obs_data: Data on which the model is fit.
model_fits: Logical scalar indicating whether to return the fitted models. The default is FALSE.