docs: def find_tx_sender(provider: Provider, raw_tx: dict) -> str:
      '''find transaction sender, vin[0] is used in this case.'''
  
      vin = raw_tx["vin"][0]
      txid = vin["txid"]
      index = vin["vout"]
      return provider.getrawtransaction(txid, 1)["vout"][index]["scriptPubKey"]["addresses"][0]