func ParseFile(file string) (*RuleGroups, []error) {
	b, err := ioutil.ReadFile(file)
	if err != nil {
		return nil, []error{err}
	}
	return Parse(b)
}
func ParseFile(file string) (*RuleGroups, []error) {
	b, err := ioutil.ReadFile(file)
	if err != nil {
		return nil, []error{err}
	}
	return Parse(b)
}
// ParseFile reads and parses rules from a file.