protected override IEnumerable <SyntaxNode> SelectMatchingDeclarations(
     SyntaxNodeAndSemanticModel <TypeBlockSyntax> container, ISet <SyntaxKind> kinds) =>
 container.SyntaxNode.DescendantNodes(IsNodeContainerTypeDeclaration)
 .Where(node => kinds.Contains(node.Kind()));
 protected abstract IEnumerable <SyntaxNode> SelectMatchingDeclarations(
     SyntaxNodeAndSemanticModel <TOwnerOfSubnodes> container,
     ISet <TSyntaxKind> kinds);