code: def write_acceptance_fraction(self, acceptance_fraction):
          
          group = self.sampler_group + '/acceptance_fraction'
          try:
              self[group][:] = acceptance_fraction
          except KeyError:
              # dataset doesn't exist yet, create it
              self[group] = acceptance_fraction
docs: Write acceptance_fraction data to file. Results are written to
          the ``[sampler_group]/acceptance_fraction``.
  
          Parameters
          -----------
          acceptance_fraction : numpy.ndarray
              Array of acceptance fractions to write.