How can I get the refresh rate via ADB? How can I use ADB to get the refresh rate of a device's screen? 

For context: I'm working on a python script that is going to display how many dropped frames occurred while it was measuring. In order to calculate that, I need to know the expected refresh rate of the device's screen.
You can get the refresh rate through this command:

adb shell dumpsys display | grep -i mphys | cut -d ',' -f 2


Note that dumpsys display mentions refresh rate at other places too. 

Derived from chr0m4k3y's answer on Stack Overflow.