How to Check if You're on Partition Slot A or Slot B?

I am trying to root my Xiaom mi a2 phone But i am stuck on changing the active partition When i enter fastboot set_active b it doesnt

I hoped I could find a phone that had an sd card slot and headphone jack but active on the screen, in the name of battery my Bluetooth connection buffers

fastboot change slot stack trace: Error: failed to set active slot: Error: {error:{code:1,cmd:fastboot --set-active=b},stderr: waiting for any device >

fastboot getvar currentslot 1 Switching the slot using fastboot Switching the slot via fastboot works if TWRP is installed in the boot partition · 2 Switching the slot