You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: 20201001204705_last_seen_ts_ip.go
    path of file: ./repos/dendrite/userapi/storage/postgres/deltas
    
    the code of the file until where you have to start completion: package deltas

import (
	"context"
	"database/sql"
	"fmt"
)

func UpLastSeenTSIP(ctx context.Co
    
func DownLastSeenTSIP(ctx context.Context, tx *sql.Tx) error {
	_, err := tx.ExecContext(ctx, `
	ALTER TABLE userapi_devices DROP COLUMN last_seen_ts;
	ALTER TABLE userapi_devices DROP COLUMN ip;
	ALTER TABLE userapi_devices DROP COLUMN user_agent;`)
	if err != nil {
		return fmt.Errorf("failed to execute downgrade: %w", err)
	}
	return nil
}