def write_acceptance_fraction(self, acceptance_fraction):
        """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.
        """
        group = self.sampler_group + '/acceptance_fraction'
        try:
            self[group][:] = acceptance_fraction
        except KeyError:
            # dataset doesn't exist yet, create it
            self[group] = acceptance_fraction
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.