private IEnumerable <RegexMutation> FindMutants(RegexNode regexNode, RegexNode root)
{
return(_mutatorsByRegexNodeType
.Where(item => regexNode.GetType() == item.Key || regexNode.GetType().IsSubclassOf(item.Key))
.SelectMany(item => item.Value)
.SelectMany(mutator => mutator.Mutate(regexNode, root)));
}