I use in Pharo 2.0  the class FileSystem to write in a text file(csv format).  I find only two options writeStream and readStream.  I would not like each time to overwrite the contents of my file and I do not find the option appendStream. How can I do?

working := FileSystem disk workingDirectory.
stream := (working / 'test.csv') writeStream

stream nextPutAll: 'something'.
stream nextPutAll: ';' .
stream nextPutAll: 'other'.

stream close.

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Hayatou