code: def controlled_mc(self, sigma):
          
          _, Q_sigma = self.RQ_sigma(sigma)
          return MarkovChain(Q_sigma)
docs: Returns the controlled Markov chain for a given policy `sigma`.
  
          Parameters
          ----------
          sigma : array_like(int, ndim=1)
              Policy vector, of length n.
  
          Returns
          -------
          mc : MarkovChain
              Controlled Markov chain.