The `script_sig` property required for the txin type?

I’m using Bitcoin Last Crate to build my own CLI wallet.

With my features I’m building TxInfor me Transactionit’s actually script_sig Do you need it in the following steps? Or do you enter it when you sign the transaction in a later step?

let txins: Vec = selected_utxos
        .iter()
        .map(|utxo| TxIn {
            previous_output: bitcoin::OutPoint {
                txid: bitcoin::Txid::from_str(&utxo.txid).expect("Invalid txid format"),
                vout: utxo.vout,
            },
            script_sig: ScriptBuf::new(),
            sequence: Sequence::MAX,
            witness: Witness::new(),
        })
        .collect();

Is it okay to put it on? ScriptBuf::new() As a placeholder?