private void AssertDependencyValidity(DataDependency <TContents> item)
{
if (item == null)
{
throw new ArgumentNullException(nameof(item));
}
if (item.Dependant != null)
{
throw new ArgumentException("Stack dependency was already added to another node.");
}
if (item.Any(n => n.Node.ParentGraph != _owner.ParentGraph))
{
throw new ArgumentException("Dependency contains data sources from another graph.");
}
}
