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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 attr(self, name, lineno=None):
 """Return an attribute node for the current extension. This is useful to pass constants on extensions to generated template code. :: self.attr('_my_attribute', lineno=lineno) """

        return nodes.ExtensionAttribute(self.identifier, name, lineno=lineno)