public void RevisionMultipleReferenceStatementError()
        {
            RevisionStatement TestRevision = new RevisionStatement("1997-09-02");

            TestRevision.AddStatement(new ReferenceStatement());
            Assert.Throws <ArgumentOutOfRangeException>(() => TestRevision.AddStatement(new ReferenceStatement()));
        }
        public void RevisionMultipleDescriptionStatementError()
        {
            RevisionStatement TestRevision = new RevisionStatement("1997-09-02");

            TestRevision.AddStatement(new YangInterpreter.Statements.DescriptionStatement());
            Assert.Throws <ArgumentOutOfRangeException>(() => TestRevision.AddStatement(new YangInterpreter.Statements.DescriptionStatement()));
        }