formToKeep: For example, if formToKeep is "purchase", then submissions["purchase"] will not be cleared, but the rest will. If formsToKeep is null or empty string, then all will be cleared.
formsToKeep: For example, if formsToKeep is ["purchase", "foobar"], then submissions["purchase"] and submissions["foobar"] will not be cleared, but the rest will. If formsToKeep is empty, then all will be cleared.
Handles null safely and correctly
Written in the D programming language.