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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 endnodes(self):
 """|Nodes| object containing all |Node| objects currently handled by the |HydPy| object which define a downstream end point of a network."""

        endnodes = devicetools.Nodes()
        for node in self.nodes:
            for element in node.exits:
                if ((element in self.elements) and
                        (node not in element.receivers)):
                    break
            else:
                endnodes += node
        return endnodes