text: import logging
  import os
  
  import numpy as np
  import pandas as pd
  
  from tardis.plasma.properties.base import (
      PreviousIterationProperty,
      ProcessingPlasmaProperty,
  )
  from tardis.plasma.properties.ion_population import PhiSahaNebular
  
  __all__ = [
      "PreviousElectronDensities",
      "PreviousBetaSobolev",
      "HeliumNLTE",
      "HeliumNumericalNLTE",
  ]
  
  logger = logging.getLogger(__name__)
  
  
  class PreviousElectronDensities(PreviousIterationProperty):
      """
      Attributes
      ----------
      previous_electron_densities : The values for the electron densities converged upon in the previous iteration.
      """
  
      outputs = ("previous_electron_densities",)
  
      def set_initial_value(self, kwargs):
          initial_value = pd.Series(
              1000000.0,
              index=kwargs["abundance"].columns,
          )
          self._set_initial_value(initial_value)
  
  
  class PreviousBetaSobolev(PreviousIterationProperty):
      """
      Attributes
      ----------
      previous_beta_sobolev : The beta sobolev values converged upon in the previous iteration.
      """
  
      outputs = ("previous_beta_sobolev",)
  
      def set_initial_value(self, kwargs):
          initial_value = pd.DataFrame(
              1.0,
              index=kwargs["atomic_data"].lines.index,
              columns=kwargs["abundance"].columns,
          )
          self._set_initial_value(initial_value)
  
  
  class HeliumNLTE(ProcessingPlasmaProperty):
      outputs = ("helium_population",)
  
      @staticmethod
      def calculate(
          level_boltzmann_factor,
          ionization_data,
          beta_rad,
          g,
          g_electron,
          w,
          t_rad,
          t_electrons,
          delta,
          zeta_data,
          number_density,
          partition_function,
      ):
          """
          Updates all of the helium level populations according to the helium NLTE recomb approximation.
          """
          helium_population = level_boltzmann_factor.loc[2].copy()
          # He I excited states
          he_one_population = HeliumNLTE.calculate_helium_one(
              g_electron, beta_rad, ionization_data, level_boltzmann_factor, g, w
          )
          helium_population.loc[0].update(he_one_population)
          # He I ground state
          helium_population.loc[0, 0] = 0.0
          # He II excited states
          he_two_population = level_boltzmann_factor.loc[2, 1].mul(
              (g.loc[2, 1, 0] ** (-1.0))
          )
          helium_population.loc[1].update(he_two_population)
          # He II ground state
          helium_population.loc[1, 0] = 1.0
          # He III states
          helium_population.loc[2, 0] = HeliumNLTE.calculate_helium_three(
              t_rad,
              w,
              zeta_data,
              t_electrons,
              delta,
              g_electron,
              beta_rad,
              ionization_data,
              g,
          )
          #        unnormalised = helium_population.sum()
          #        normalised = helium_population.mul(number_density.ix[2] / unnormalised)
          #        helium_population.update(normalised)
          return helium_population
  
      @staticmethod
      def calculate_helium_one(
          g_electron, beta_rad, ionization_data, level_boltzmann_factor, g, w
      ):
          """
          Calculates the He I level population values, in equilibrium with the He II ground state.
          """
          return (
              level_boltzmann_factor.loc[2, 0]
              * (1.0 / (2 * g.loc[2, 1, 0]))
              * (1 / g_electron)
              * (1 / (w**2.0))
              * np.exp(ionization_data.loc[2, 1] * beta_rad)
          )
  
      @staticmethod
      def calculate_helium_three(
          t_rad,
          w,
          zeta_data,
          t_electrons,
          delta,
          g_electron,
          beta_rad,
          ionization_data,
          g,
      ):
          """
          Calculates the He III level population values.
          """
          zeta = PhiSahaNebular.get_zeta_values(zeta_data, 2, t_rad)[1]
          he_three_population = (
              2
              * (float(g.loc[2, 2, 0]) / g.loc[2, 1, 0])
              * g_electron
              * np.exp(-ionization_data.loc[2, 2] * beta_rad)
              * w
              * (delta.loc[2, 2] * zeta + w * (1.0 - zeta))
              * (t_electrons / t_rad) ** 0.5
          )
          return he_three_population
  
  
  class HeliumNumericalNLTE(ProcessingPlasmaProperty):
      """
      IMPORTANT: This particular property requires a specific numerical NLTE
      solver and a specific atomic dataset (neither of which are distributed
      with Tardis) to work.
      """
  
      outputs = ("helium_population",)
  
      def __init__(self, plasma_parent, heating_rate_data_file):
          super(HeliumNumericalNLTE, self).__init__(plasma_parent)
          self._g_upper = None
          self._g_lower = None
          self.heating_rate_data = np.loadtxt(heating_rate_data_file, unpack=True)
  
      def calculate(
          self,
          ion_number_density,
          electron_densities,
          t_electrons,
          w,
          lines,
          j_blues,
          levels,
          level_boltzmann_factor,
          t_rad,
          zeta_data,
          g_electron,
          delta,
          partition_function,
          ionization_data,
          beta_rad,
          g,
          time_explosion,
      ):
          logger.info("Performing numerical NLTE He calculations.")
          if len(j_blues) == 0:
              return None
          # Outputting data required by SH module
          for zone, _ in enumerate(electron_densities):
              with open(
                  f"He_NLTE_Files/shellconditions_{zone}.txt", "w"
              ) as output_file:
                  output_file.write(ion_number_density.loc[2].sum()[zone])
                  output_file.write(electron_densities[zone])
                  output_file.write(t_electrons[zone])
                  output_file.write(self.heating_rate_data[zone])
                  output_file.write(w[zone])
                  output_file.write(time_explosion)
                  output_file.write(t_rad[zone])
                  output_file.write(self.plasma_parent.v_inner[zone])
                  output_file.write(self.plasma_parent.v_outer[zone])
  
          for zone, _ in enumerate(electron_densities):
              with open(
                  f"He_NLTE_Files/abundances_{zone}.txt", "w"
              ) as output_file:
                  for element in range(1, 31):
                      try:
                          number_density = (
                              ion_number_density[zone].loc[element].sum()
                          )
                      except:
                          number_density = 0.0
                          logger.debug(
                              f"Number Density could not be calculated. Setting Number Density to {number_density}"
                          )
                      output_file.write(number_density)
  
              helium_lines = lines[lines["atomic_number"] == 2]
              helium_lines = helium_lines[helium_lines["ion_number"] == 0]
          for zone, _ in enumerate(electron_densities):
              with open(
                  f"He_NLTE_Files/discradfield_{zone}.txt", "w"
              ) as output_file:
                  j_blues = pd.DataFrame(j_blues, index=lines.index)
                  helium_j_blues = j_blues[zone].loc[helium_lines.index]
                  for value in helium_lines.index:
                      if helium_lines.level_number_lower.loc[value] < 35:
                          output_file.write(
                              int(helium_lines.level_number_lower.loc[value] + 1),
                              int(helium_lines.level_number_upper.loc[value] + 1),
                              j_blues[zone].loc[value],
                          )
          # Running numerical simulations
          for zone, _ in enumerate(electron_densities):
              os.rename(
                  f"He_NLTE_Files/abundances{zone}.txt",
                  "He_NLTE_Files/abundances_current.txt",
              )
              os.rename(
                  f"He_NLTE_Files/shellconditions{zone}.txt",
                  "He_NLTE_Files/shellconditions_current.txt",
              )
              os.rename(
                  f"He_NLTE_Files/discradfield{zone}.txt",
                  "He_NLTE_Files/discradfield_current.txt",
              )
              os.system("nlte-solver-module/bin/nlte_solvertest >/dev/null")
              os.rename(
                  "He_NLTE_Files/abundances_current.txt",
                  f"He_NLTE_Files/abundances{zone}.txt",
              )
              os.rename(
                  "He_NLTE_Files/shellconditions_current.txt",
                  f"He_NLTE_Files/shellconditions{zone}.txt",
              )
              os.rename(
                  "He_NLTE_Files/discradfield_current.txt",
                  f"He_NLTE_Files/discradfield{zone}.txt",
              )
              os.rename("debug_occs.dat", f"He_NLTE_Files/occs{zone}.txt")
          # Reading in populations from files
          helium_population = level_boltzmann_factor.loc[2].copy()
          for zone, _ in enumerate(electron_densities):
              with open(
                  f"He_NLTE_Files/discradfield{zone}.txt", "r"
              ) as read_file:
                  for level in range(0, 35):
                      level_population = read_file.readline()
                      level_population = float(level_population)
                      helium_population[zone].loc[0, level] = level_population
                  helium_population[zone].loc[1, 0] = float(read_file.readline())
          # Performing He LTE level populations (upper two energy levels,
          # He II excited states, He III)
          he_one_population = HeliumNLTE.calculate_helium_one(
              g_electron,
              beta_rad,
              partition_function,
              ionization_data,
              level_boltzmann_factor,
              electron_densities,
              g,
              w,
              t_rad,
              t_electrons,
          )
          helium_population.loc[0, 35].update(he_one_population.loc[35])
          helium_population.loc[0, 36].update(he_one_population.loc[36])
  
          he_two_population = level_boltzmann_factor.loc[2, 1, 1:].mul(
              (g.loc[2, 1, 0] ** (-1)) * helium_population.loc[s1, 0]
          )
          helium_population.loc[1, 1:].update(he_two_population)
  
          helium_population.loc[2, 0] = HeliumNLTE.calculate_helium_three(
              t_rad,
              w,
              zeta_data,
              t_electrons,
              delta,
              g_electron,
              beta_rad,
              partition_function,
              ionization_data,
              electron_densities,
          )
          unnormalised = helium_population.sum()
          normalised = helium_population.mul(
              ion_number_density.loc[2].sum() / unnormalised
          )
          helium_population.update(normalised)
          return helium_population
  