A character vector of one or more keywords to be looked up in the ICD descriptions, e.g., "cardio", c("cardio", "lymphoma"). Each keyword can be a regular expression, e.g. "lymph*".
icd.version
The ICD version (or revision) number, 9 or 10. Default = 10.
ignore.case
If `TRUE` (default), case is ignored during matching; if `FALSE`, the matching is case sensitive.