internal AbstractBufferedWriter StartPureValuesFile(out uint fileId)
{
var fId = FileCollection.AddFile("pvl");
fileId = fId.Index;
var pureValues = new FilePureValues(FileCollection.NextGeneration(), FileCollection.Guid);
var writer = fId.GetAppenderWriter();
FileCollection.SetInfo(fId.Index, pureValues);
pureValues.WriteHeader(writer);
return(writer);
}