Tree Mapper Mapping Link not working

Hi, I am trying to use make a demo of Tree Mapper using angular 8 but while doing so, I could not map the nodes as it says the error which has been attached in a screenshot. Is there a way to overcome this?

The Mapping Link Code:


There isn’t enough information for me to tell. What changes have you made from the code in the sample?

made it to work, actually some js code was needed to be converted to typescript with defined type…it worked…thanks