Request preprepare

def _request_prepare(self, three_pc_key: Tuple[int, int],
                         recipients: List[str] = None,
                         stash_data: Optional[Tuple[str, str, str]] = None) -> bool:
        """
        Request preprepare
        """
        if recipients is None:
            recipients = self.node.nodestack.connecteds.copy()
            primaryName = self.primaryName[:self.primaryName.rfind(":")]
            recipients.discard(primaryName)
        return self._request_three_phase_msg(three_pc_key, self.requested_prepares, PREPARE, recipients, stash_data)