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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 constraint(self, n=-1, fid=0):
 """Obtain the set of orthogonal equations that make the solution of the rank deficient normal equations possible. :param fid: the id of the sub-fitter (numerical) """

        c = self._getval("constr", fid)
        if n < 0 or n > self.deficiency(fid):
            return c
        else:
            raise RuntimeError("Not yet implemented")