How to change the current active partition slot?

How to change the current active partition slot? fastboot set active slot stack trace: Error: failed to set active slot: Error: {error:{code:1,cmd:fastboot --set-active=b},stderr: waiting for any device > fastboot get active slot slot fastboot getvar current-slot fastboot getvar all Get active system slot slot fastboot

fastboot get active slot zip package flashall: Flash all partitions from $ANDROID_PRODUCT_OUT On AB devices, flashed slot is set as active Secondary images may be

fastboot set active slot In this video, I will be discussing how to fix the Fastboot OEM Unlock Waiting for any device try setting the slots again, without the space between -- It will return fastboot --set-active:a fastboot: unknown option – set-active:a