def METHOD_NAME(self, cmd):
    self._process = sp.Popen(cmd, stdout=sp.PIPE)
    while True:
        ret = self._process.poll()
        if ret is not None:
            if ret == self.successretcode:
                out = self._process.communicate()[0].strip().decode('utf8')
                self.selection = self._split_output(out)
                self._handle_selection(self.selection)
                return self.selection
            else:
                return None
        time.sleep(0.1)