private bool TryGetDiagramConnectorViewModel(ModelRelationshipId modelRelationshipId, out DiagramConnectorViewModel viewModel)
 => _diagramConnectorToViewModelMap.TryGet(modelRelationshipId, out viewModel);
 private bool TryGetDiagramConnectorViewModel(IDiagramConnector diagramConnector, out DiagramConnectorViewModel viewModel)
 => _diagramConnectorToViewModelMap.TryGet(diagramConnector, out viewModel);