docs: def determine_frame_positions(self):
          """Record the file pointer position of each frame"""
          self.rewind_file()
          with ignored(struct.error):
              while True:
                  pointer_position = self.blob_file.tell()
                  length = struct.unpack('<i', self.blob_file.read(4))[0]
                  self.blob_file.seek(length - 4, 1)
                  self.frame_positions.append(pointer_position)
          self.rewind_file()
          log.info("Found {0} frames.".format(len(self.frame_positions)))