code: def export_bert(data, electrodes, filename):
      if has_multiple_timesteps(data):
          for i, timestep in enumerate(split_timesteps(data)):
              export_bert(timestep, electrodes,
                          filename.replace(".", "_%.3d." % i))
      f = open(filename, 'w')
      f.write("%d\n" % len(electrodes))
      f.write("
      electrodes = electrodes.copy()
      data = data.copy()
      electrodes.columns = electrodes.columns.str.lower()
      data.columns = data.columns.str.lower()
      cols_to_export = ["a", "b", "m", "n", "u", "i", "r", "rho_a", "error"]
      data.drop(data.columns.difference(cols_to_export), 1, inplace=True)
      data.rename(columns={"rho_a": "rhoa", "error": "err"}, inplace=True)
      for key in electrodes.keys():
          f.write("%s " % key)
      f.write("\n")
      for row in electrodes.itertuples(index=False):
          for val in row:
              f.write("%5.3f " % val)
          f.write("\n")
      f.write("%d\n" % len(data))
      f.write("
      columns = data.columns.tolist()
      for c in "abmn":
          columns.remove(c)
      columns = list("abmn") + columns
      data = data[columns]
      for key in data.keys():
          f.write("%s " % key)
      f.write("\n")
      for row in data.itertuples(index=False):
          for i, val in enumerate(row):
              if i < 4:
                  f.write("%d " % val)
              else:
                  f.write("%E " % val)
          f.write("\n")
      f.close()