You can use ffmpeg's concat filter to join the two videos into a single file:
// Create files list
echo file file1.mp4 >  mylist.txt 
echo file file2.mp4 >> mylist.txt
// Concatenate files
ffmpeg -f concat -i mylist.txt -c copy output.mp4
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence