docs: def simple_spool_transaction(self, from_address, to, op_return, min_confirmations=6):
          """
          Utililty function to create the spool transactions. Selects the inputs,
          encodes the op_return and constructs the transaction.
  
          Args:
              from_address (str): Address originating the transaction
              to (str): list of addresses to receive tokens (file_hash, file_hash_metadata, ...)
              op_return (str): String representation of the spoolverb, as returned by the properties of Spoolverb
              min_confirmations (int): Number of confirmations when chosing the inputs of the transaction. Defaults to 6
  
          Returns:
              str: unsigned transaction
  
          """
          # list of addresses to send
          ntokens = len(to)
          nfees = old_div(self._t.estimate_fee(ntokens, 2), self.fee)
          inputs = self.select_inputs(from_address, nfees, ntokens, min_confirmations=min_confirmations)
          # outputs
          outputs = [{'address': to_address, 'value': self.token} for to_address in to]
          outputs += [{'script': self._t._op_return_hex(op_return), 'value': 0}]
          # build transaction
          unsigned_tx = self._t.build_transaction(inputs, outputs)
          return unsigned_tx