bitcoinjs-lib: Using string signature not working!

I have a a PSBT built and a Signature string, is there any way to apply the signature to the inputs?

  const psbt = new bitcoinjs.Psbt({ network: network });
/*
Here i add inputs and outputs

e.g.:  psbt.addInput({
        hash: element.identifier,
        index: inputIndex,
        // VERY IMPORTANT
        nonWitnessUtxo: Buffer.from(
          element.raw,
          'base64',
        ),
      });

*/

  let signature = // String recieved from other api

// Doesn't work
    psbt.signAllInputs(signature);
    psbt.finalizeAllInputs();