docs: def write_output_files(self,traj):
          """
          The total hydrogen bond count per frame is provided as CSV output file.
          Each trajectory has a separate file.
          """
          try:
              os.chdir("analysis")
          except Exception as e:
              os.mkdir("analysis")
              os.chdir("analysis")
          os.mkdir("pistacking")
          os.chdir("pistacking")
          with open('pistacking_data_total_'+str(traj)+'.csv', 'wb') as outfile:
              hwriter = csv.writer(outfile, delimiter=' ')
              for time in self.pistacking_by_time[traj]:
                  hwriter.writerow([time[0],time[1]])
          for bond in self.pistacking_by_type[traj]:
              if bond in self.pi_contacts_for_drawing.keys():
                  with open("pi_contact_"+str(traj)+".csv","wb") as outfile:
                      hwriter = csv.writer(outfile, delimiter=' ')
                      for time in self.timesteps:
                          result = [1 if x[0]==time and x["acceptor_idx"]==bond["acceptor_idx"] else 0 for x in self.timeseries][0]
                          hwriter.writerow([time,result])
          os.chdir("../../")