Allow a user to query a device directly using XML-requests.

        :param rpc_command: (str) rpc command such as:
                                  <Get><Operational><LLDP><NodeTable></NodeTable></LLDP></Operational></Get>

def make_rpc_call(self, rpc_command):
        """
        Allow a user to query a device directly using XML-requests.

        :param rpc_command: (str) rpc command such as:
                                  <Get><Operational><LLDP><NodeTable></NodeTable></LLDP></Operational></Get>
        """
        # ~~~ hack: ~~~
        if not self.is_alive():
            self.close()  # force close for safety
            self.open()  # reopen
        # ~~~ end hack ~~~
        result = self._execute_rpc(rpc_command)
        return ET.tostring(result)