error: import has a duplicated items for rule: a.sml
--> main.sml:1:14
     |
   1 | Import(rules=['a.sml', 'a.sml', 'a.sml'])
     |               ^ first import attempted here
~~~ 2 duplicate(s) found here
--> (1) main.sml:1:23
     |
   1 | Import(rules=['a.sml', 'a.sml', 'a.sml'])
     |                        ^
--> (2) main.sml:1:32
     |
   1 | Import(rules=['a.sml', 'a.sml', 'a.sml'])
     |                                 ^