assert                  Raises error if predicate is FALSE in any
                        columns selected
assertr                 assertr: Assertive programming for R analysis
                        pipeline.
in_set                  Returns TRUE if value in set
insist                  Raises error if dynamically created predicate
                        is FALSE in any columns selected
not_na                  Returns TRUE if value is not NA
verify                  Raises error if expression is FALSE anywhere
within_bounds           Creates bounds checking predicate
within_n_sds            Return a function to create z-score checking
                        predicate
