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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 xtqx(self):
 """get the normal matrix attribute. Create the attribute if it has not yet been created Returns ------- xtqx : pyemu.Matrix """

        if self.__xtqx is None:
            self.log("xtqx")
            self.__xtqx = self.jco.T * (self.obscov ** -1) * self.jco
            self.log("xtqx")
        return self.__xtqx