private static Solution UpdateMainDocument(Document document, SyntaxNode root, MethodDeclarationSyntax method, IEnumerable<IGrouping<Document, ReferenceLocation>> documentGroups)
 {
     var mainDocGroup = documentGroups.FirstOrDefault(dg => dg.Key.Equals(document));
     SyntaxNode newRoot;
     if (mainDocGroup == null)
     {
         newRoot = root.ReplaceNode(method, method.AddModifiers(staticToken));
     }
     else
     {
         var diagnosticNodes = mainDocGroup.Select(referenceLocation => root.FindNode(referenceLocation.Location.SourceSpan)).ToList();
         newRoot = root.TrackNodes(diagnosticNodes.Union(new[] { method }));
         newRoot = newRoot.ReplaceNode(newRoot.GetCurrentNode(method), method.AddModifiers(staticToken));
         foreach (var diagnosticNode in diagnosticNodes)
         {
             var token = newRoot.FindToken(diagnosticNode.GetLocation().SourceSpan.Start);
             var tokenParent = token.Parent;
             if (token.Parent.IsKind(SyntaxKind.IdentifierName)) continue;
             var invocationExpression = newRoot.GetCurrentNode(diagnosticNode).FirstAncestorOrSelfOfType<InvocationExpressionSyntax>()?.Expression;
             if (invocationExpression == null || invocationExpression.IsKind(SyntaxKind.IdentifierName)) continue;
             var memberAccess = invocationExpression as MemberAccessExpressionSyntax;
             if (memberAccess == null) continue;
             var newMemberAccessParent = memberAccess.Parent.ReplaceNode(memberAccess, memberAccess.Name)
                 .WithAdditionalAnnotations(Formatter.Annotation);
             newRoot = newRoot.ReplaceNode(memberAccess.Parent, newMemberAccessParent);
         }
     }
     var newSolution = document.Project.Solution.WithDocumentSyntaxRoot(document.Id, newRoot);
     return newSolution;
 }