filters.go
func ApplyRuleIf(condition, rule Ruler) Ruler {
	return &apply{
		condition: condition,
		rule:      rule,
	}
}
func ApplyRuleIf(condition, rule Ruler) Ruler {
	return &apply{
		condition: condition,
		rule:      rule,
	}
}
// ApplyRuleIf test if condition is true than apply rule. If condition is false
// do nothing, return true.