code: def return_hdr(self):
          
          hdr = {}            
          hdr['s_freq'] = self.s_freq
          hdr['chan_name'] = ['RRi']
          
          with open(self.filename, 'rt') as f:
              head = [next(f) for x in range(12)]
              hdr['subj_id'] = head[0][11:-3]
              hdr['start_time'] = DEFAULT_DATETIME
              hdr['recorder'] = head[2][10:]
              hdr['s_freq_ecg'] = int(head[3][4:]) # ECG sampling frequency
              t = datetime.strptime(head[4][16:24], '%H:%M:%S')
              hdr['total_dur'] = timedelta(hours=t.hour, minutes=t.minute, 
                 seconds=t.second)
              hdr['export_date'] = DEFAULT_DATETIME
              hdr['data_type'] = head[10][11:]
              
              for i, _ in enumerate(f):
                  pass
              hdr['n_samples'] = i
          
          output = (hdr['subj_id'], hdr['start_time'], hdr['s_freq'], 
                    hdr['chan_name'], hdr['n_samples'], hdr)
          
          return output
docs: Return the header for further use.
  
          Returns
          -------
          subj_id : str
              subject identification code
          start_time : datetime
              start time of the dataset
          s_freq : float
              sampling frequency
          chan_name : list of str
              list of all the channels
          n_samples : int
              number of samples in the dataset
          orig : dict
              the full header