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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _dfs(self, visited):
 """ Adds the job and all jobs reachable on a directed path from current node to the given set. """

        if self not in visited:
            visited.add(self)
            for successor in self._children + self._followOns:
                successor._dfs(visited)