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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def init_cursor(self):
 """Position the cursor appropriately. The cursor is set to either the beginning of the oplog, or wherever it was last left off. Returns the cursor and True if the cursor is empty. """

        timestamp = self.read_last_checkpoint()

        if timestamp is None or self.only_dump:
            if self.collection_dump:
                # dump collection and update checkpoint
                timestamp = self.dump_collection()
                if self.only_dump:
                    LOG.info("Finished dump. Exiting.")
                    timestamp = None
                    self.running = False

                self.update_checkpoint(timestamp)
                if timestamp is None:
                    return None, True
            else:
                # Collection dump disabled:
                # Return cursor to beginning of oplog but do not set the
                # checkpoint. The checkpoint will be set after an operation
                # has been applied.
                cursor = self.get_oplog_cursor()
                return cursor, self._cursor_empty(cursor)

        cursor = self.get_oplog_cursor(timestamp)
        cursor_empty = self._cursor_empty(cursor)

        if cursor_empty:
            # rollback, update checkpoint, and retry
            LOG.debug("OplogThread: Initiating rollback from " "get_oplog_cursor")
            self.update_checkpoint(self.rollback())
            return self.init_cursor()

        first_oplog_entry = next(cursor)

        oldest_ts_long = util.bson_ts_to_long(self.get_oldest_oplog_timestamp())
        checkpoint_ts_long = util.bson_ts_to_long(timestamp)
        if checkpoint_ts_long < oldest_ts_long:
            # We've fallen behind, the checkpoint has fallen off the oplog
            return None, True

        cursor_ts_long = util.bson_ts_to_long(first_oplog_entry["ts"])
        if cursor_ts_long > checkpoint_ts_long:
            # The checkpoint is not present in this oplog and the oplog
            # did not rollover. This means that we connected to a new
            # primary which did not replicate the checkpoint and which has
            # new changes in its oplog for us to process.
            # rollback, update checkpoint, and retry
            LOG.debug(
                "OplogThread: Initiating rollback from "
                "get_oplog_cursor: new oplog entries found but "
                "checkpoint is not present"
            )
            self.update_checkpoint(self.rollback())
            return self.init_cursor()

        # first entry has been consumed
        return cursor, cursor_empty