I want to know the implementation of
http://127.0.0.1:8080/blocks/head endpoint from (https://github.com/paritytech/substrate-api-sidecar)
I found some interface here https://github.com/polkadot-js/api/blob/master/packages/rpc-augment/src/augment/jsonrpc.ts#L85 and some implementation https://github.com/polkadot-js/api/blob/master/packages/api-derive/src/chain/getHeader.ts
but this function doesn't makes sense to me. lack of RxJS understanding I guess. can anyone give me a good direction? I want to see the actual implementation of that particular API...