outcomeCov_var: A list of individual baseline variables used in final model
where_var: Variables used in where conditions used in subsetting the data used in final analysis (where_case), the variables not included in the final model
use_censor: Use censoring for per-protocol analysis - censor person-times once a person-trial stops taking the initial treatment value
maxperiod: Maximum period
minperiod: Minimum period
keeplist: A list contains names of variables used in final model