[vtkusers] reading a collection of polydata

[Dean Inglis]

I subclassed vtkPolyDataAlgorithm to make a reader for
text files containg sequences of x-y pairs that represent
2D contours.  There are generally more than one contour 
specified per file.  Currenly I read in each contour and append
it with vtkAppendPolyData.  The output of the reader is then
one polydata with its number of cells equal to the number of
contours.  Further on in my app, I split them back out with
vtkExtractSelectedPolyDataIds and add them to a vtkPolyDataCollection.
 
What I really want is to have the output of the 
reader to be a vtkPolyDataCollection so that each contour can
be uniquely retrieved directly from the reader, however, I cant
find the appropriate parent class that would allow either multiple
outputs to be specified on the fly during RequestData(...) or
to have the one output be a vtkPolyDataCollection.   That is,
there is no parent class named vtkCollectionAlgorithm that specifies
a collection as its output.  Any design ideas to deal with this
scenario would be greatly appeciated.

thanks,
Dean