code: def run_mcmc(self, niterations):
          
          pos = self._pos
          if pos is None:
              pos = self._p0
          res = self._sampler.run_mcmc(pos, niterations)
          p, _, _ = res[0], res[1], res[2]
          # update the positions
          self._pos = p
docs: Advance the ensemble for a number of samples.
  
          Parameters
          ----------
          niterations : int
              Number of samples to get from sampler.