code: def get_total_size_trans(self, entries):
          
          size = 0
          for entry in entries:
              if entry['response']['_transferSize'] > 0:
                  size += entry['response']['_transferSize']
          return size
docs: Returns the total size of a collection of entries - transferred.
  
          NOTE: use with har file generated with chrome-har-capturer
  
          :param entries: ``list`` of entries to calculate the total size of.