def METHOD_NAME(
    cls, definitions: dict
) -> typing.Generator[Rule, None, None]:
    """Generator that parses a dictionary of severity rules as loaded from a YAML
    config file, and yields a chain of rules with matching expressions and
    corresponding severity modifiers.
    """
    default = definitions.get("default-severity")
    if default is None:
        # Use the alert's original severity value
        yield (), lambda x: Severity(x)
    else:
        default = Severity(default)
        yield (), lambda x: default
    yield from cls._parse_rule_sublist((), definitions.get("rules", []))