Received Signal Strength Indication, from 0 to 4 bars.

def rssi_bars(self) -> int:
        """Received Signal Strength Indication, from 0 to 4 bars."""
        rssi_db = self.rssi_db
        if rssi_db < 45:
            return 0
        elif rssi_db < 60:
            return 1
        elif rssi_db < 75:
            return 2
        elif rssi_db < 90:
            return 3
        return 4