The getlevel method does not work for geojson files created without @relations tags. Here is the example of two levels 1 & 2 file:https://gist.githubusercontent.com/akarsh/a92d1c3be234ab1ff7d2469d511ad03a/raw/f483daa278647c5353a784f0081423474cfc7f17/bothlevels.geojson Created using JOSM and following simple indoor tagging.