Using a class varilable instead of temp files for keeping track of docs. :meth:`IpythonDirective.setup` method was using a temporary file, such as :file:`/tmp/seen_docRANDOM`, for storing visited source document filenames. For a document that is not visited (name not in the temporary file), it restarts counting line numbers. Temporary file names are selected randomly and they were not deleted from the disk upon completion of a build. Since :meth:`.setup` picks a temp file arbitrarily to visited status of a file is determined incorrectly. Using a class variable resolves this problem. Changed the directive setup function to use a class files for keeping track of documents.