code: def sign_transaction(self, txins: Union[TxOut],
                           tx: MutableTransaction) -> MutableTransaction:
          '''sign the parent txn outputs P2PKH'''
  
          solver = P2pkhSolver(self._private_key)
          return tx.spend(txins, [solver for i in txins]f sign_transaction(self, txins: Union[TxOut],
                           tx: MutableTransaction) -> MutableTransaction:
          '''sign the parent txn outputs P2PKH'''
  
          solver = P2pkhSolver(self._private_key)
          return tx.spend(txins, [solver for i in txins])
docs: sign the parent txn outputs P2PKH