What does it mean when USPS tracking says picked up by shipping partner?

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Tags

1. #facility
2. #delivery
3. #shipped
4. #party
5. #initially
6. #another
7. #means
8. #fedex
9. #arrived
10. #third
11. #final
12. #partner
13. #carrier
14. #package
15. #shipping
16. #thread
17. #still
18. #control
19. #handed
20. #delivered