code: def condition_number(self):
          
          # Mimic x = np.matrix(self.x) (deprecated)
          x = np.atleast_2d(self.x)
          ev = np.linalg.eig(x.T @ x)[0]
          return np.sqrt(ev.max() / ev.min())
docs: Condition number of x; ratio of largest to smallest eigenvalue.