code: def X2_chain_H0(self, args):
          
          #extract parameters
          H0 = args[0]
          omega_m = self.omega_m_fixed
          Ode0 = self._omega_lambda_fixed
          logL, bool = self.prior_H0(H0)
          if bool is True:
              logL += self.LCDM_lensLikelihood(H0, omega_m, Ode0)
          return logL, None
docs: routine to compute X2 given variable parameters for a MCMC/PSO chain