json rpc – where is the implementation of the getaddressutxos method of litecoin rpc

Hello, I started to play with litecoin node and create rpc with litecoin-cli queries. There are some methods that have caught my attention and have something to do with "addressindex":

I searched them in github litecoin-project, but I did not find where the implementation was. I probably did not search in the right place or missed anything, as they say. Would you help me to find out where the code is that implements these methods? Do you have any idea why these methods are not present in Bitcoin? in my view are very useful. thank you in advance