public string GetPhysicalPath(string file) =>
 Path.IsPathRooted(file) ? file : _impl.GetPhysicalPath(file);
 public static IEnumerable <KeyValuePair <string, string> > GetAllPhysicalPaths(this IFileAbstractLayer fal) =>
 from r in fal.GetAllInputFiles()
 select new KeyValuePair <string, string>(r, fal.GetPhysicalPath(r));