message: fix: bigint -> number
diff: @@ -142,8 +142,8 @@ export async function estimateTransfer(
  }
  interface FeeEstimation {
  - fee: bigint,
  - fee_rate: bigint,
  + fee: number,
  + fee_rate: number,
  }
  interface FeeEstimateResponse {
  cost_scalar_change_by_byte: bigint,
  @@ -1353,13 +1353,17 @@ export async function sponsorTransaction(
  const sponsorPubKey = pubKeyfromPrivKey(options.sponsorPrivateKey);
  if (sponsorOptions.fee === undefined || sponsorOptions.fee === null) {
  - let txFee = BigInt(0);
  + let txFee = 0;
  switch (options.transaction.payload.payloadType) {
  case PayloadType.TokenTransfer:
  case PayloadType.SmartContract:
  case PayloadType.ContractCall:
  const estimatedLen = options.transaction.serialize().byteLength;
  + try {
  txFee = (await estimateTransaction(options.transaction.payload, estimatedLen, network))[1].fee;
  + } catch(e) {
  + throw e;
  + }
  break;
  default:
  throw new Error(
  