RPCs that return detailed information about mempool entries (e.g. `getmempoolentry` and `getrawmempool(verbose=True)` include the fields `fee`, `modifiedfee`, `descendantfees`, and `ancestorfees` which were marked as "DEPRECATED" and replaced with a `fees` object field in #12240 (since v0.17).

We should remove these fields, but first, properly deprecate them using `-deprecatedrpc`.

#### Useful skills:

- basic understanding of Bitcoin Core RPC interface

#### Want to work on this issue?

For guidance on contributing, please read [CONTRIBUTING.md](https://github.com/bitcoin/bitcoin/blob/master/CONTRIBUTING.md) before opening your pull request.

}
    if (!pblockindex) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
    }
    if (!fVerbose)
    {
        CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION);
        ssBlock << pblockindex->GetBlockHeader();
        std::string strHex = HexStr(ssBlock);
        return strHex;
    }
    return blockheaderToJSON(tip, pblockindex);
},
    };
}
static CBlock GetBlockChecked(const CBlockIndex* pblockindex)
{
    CBlock block;
    if (IsBlockPruned(pblockindex)) {
        throw JSONRPCError(RPC_MISC_ERROR, "Block not available (pruned data)");
    }
    if (!ReadBlockFromDisk(block, pblockindex, Params().GetConsensus())) {
        
        
        
        throw JSONRPCError(RPC_MISC_ERROR, "Block not found on disk");
    }
    return block;
}
static CBlockUndo GetUndoChecked(const CBlockIndex* pblockindex)