reason why deleting triples?

[EJHyun]

Hi
I'm curious about this code snippet

for i in range (len(train_triples)-1,-1,-1): # range(start, stop, step)
			if i not in keep_idx:
				del train_triples[i] 
                # if start / end time is like -405 or like 100, delete                
                # But why?

Why do you delete those train facts?