code: def seek(self, offset, whence=os.SEEK_SET):
          
  
          pos = None
          if whence == os.SEEK_SET:
              pos = self.offset + offset
          elif whence == os.SEEK_CUR:
              pos = self.tell() + offset
          elif whence == os.SEEK_END:
              pos = self.offset + self.len + offset
          else:
              raise ValueError("invalid whence {}".format(whence))
  
          if pos > self.offset + self.len or pos < self.offset:
              raise ValueError("seek position beyond chunk area")
  
          self.parent_fd.seek(pos, os.SEEK_SET)
docs: Seek to position in stream, see file.seek