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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 igetattr(self, attrname, context=None):
 """Infer the possible values of the given attribute on the slice. :param attrname: The name of the attribute to infer. :type attrname: str :returns: The inferred possible values. :rtype: iterable(NodeNG) """

        if attrname == "start":
            yield self._wrap_attribute(self.lower)
        elif attrname == "stop":
            yield self._wrap_attribute(self.upper)
        elif attrname == "step":
            yield self._wrap_attribute(self.step)
        else:
            yield from self.getattr(attrname, context=context)