code: def _to_free_energy(z, minener_zero=False):
      
      pi = _to_density(z)
      free_energy = _np.inf * _np.ones(shape=z.shape)
      nonzero = pi.nonzero()
      free_energy[nonzero] = -_np.log(pi[nonzero])
      if minener_zero:
          free_energy[nonzero] -= _np.min(free_energy[nonzero])
      return free_energy
docs: Compute free energies from histogram counts.
  
      Parameters
      ----------
      z : ndarray(T)
          Histogram counts.
      minener_zero : boolean, optional, default=False
          Shifts the energy minimum to zero.
  
      Returns
      -------
      free_energy : ndarray(T)
          The free energy values in units of kT.