public void ValidDollarReferencePatternTest(string key, int pathIndex, int keyGroup, string canonicalForm)
        {
            IPathAndGroupReference amp = new DollarReference("$" + key);

            amp.GetPathIndex().Should().Be(pathIndex);
            amp.GetKeyGroup().Should().Be(keyGroup);
            amp.GetCanonicalForm().Should().Be($"${canonicalForm}");
        }
 public DollarPathElement(string key) :
     base(key)
 {
     _dRef = new DollarReference(key);
 }