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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 _vfg_node(self, addr):
 """ Gets vfg node at @addr Returns VFGNode or None """

        for n in self._vfg._nodes.values():
            if n.addr == addr:
                return n
        raise DataGraphError("No VFG node at 0x%x" % addr)