IsEqualString tests if `sev` is of equal severity to the refererence severity `refSev`.

IsHigherString tests if `sev` is of higher severity than the refererence severity `refSev`.

IsLowerString tests if `sev` is of lower severity than the refererence severity `refSev`.

SeveritiesHigher returns a subset of the provided severities with elements that with a lower index than the provided severity.

SeveritiesLower returns a subset of the provided severities with elements that with a higher index than the provided severity.

Common severities.