code: def http_range(self) -> slice:
          
          rng = self._headers.get(hdrs.RANGE)
          start, end = None, None
          if rng is not None:
              try:
                  pattern = r'^bytes=(\d*)-(\d*)$'
                  start, end = re.findall(pattern, rng)[0]
              except IndexError:  # pattern was not found in header
                  raise ValueError("range not in acceptable format")
  
              end = int(end) if end else None
              start = int(start) if start else None
  
              if start is None and end is not None:
                  # end with no start is to return tail of content
                  start = -end
                  end = None
  
              if start is not None and end is not None:
                  # end is inclusive in range header, exclusive for slice
                  end += 1
  
                  if start >= end:
                      raise ValueError('start cannot be after end')
  
              if start is end is None:  # No valid range supplied
                  raise ValueError('No start or end of range specified')
  
          return slice(start, end, 1)
docs: The content of Range HTTP header.
  
          Return a slice instance.