What does <package_name> refer to in the adb command recommended for Firebase analytics debugging

I am trying the firebase analytics with flutter, following the example on https://firebase.google.com/docs/flutter/setup?platform=android. I am trying to start the debug view by using the command adb shell setprop debug.firebase.analytics.app <package_name>. I do not understand what <package_name> is? Can anyone tell me what it refers to?