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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 visit_slice(self, node, parent):
 """visit a Slice node by returning a fresh instance of it"""

        newnode = nodes.Slice(parent=parent)
        newnode.postinit(
            _visit_or_none(node, "lower", self, newnode),
            _visit_or_none(node, "upper", self, newnode),
            _visit_or_none(node, "step", self, newnode),
        )
        return newnode