Import error: No module named zigbee

Im trying to do a node discovery using this documentation:|_____9

The problem is that python doesnt recognise the module named zigbee. I suppose that i have to install some kind of library but I dont know which and how.

Thank you

What are you running this Python file on? It is meant to be running on a Digi X4 or X2 Gateway which has the default files on it.