HMP2020 questions (related to config hw-model and protocol)

{
  "version": "1.0",
  "options": {},
  "devices": {
    "PS": {
      "hw-type": "PS",
      "hw-model": "$MODEL",
      "communication": {
        "protocol": "$PROTOCOL",
        "port": "/dev/ttyACM0"
      }
    }
  },
  "channels": {
    "high-current": {
      "hw-type": "PS",
      "device": "PS",
      "channel": 1,
      "program": {
        "maxvoltage": 32,
        "maxcurrent": 5
      }
    },
    "low-current": {
      "hw-type": "PS",
      "device": "PS",
      "channel": 2,
      "program": {
        "maxvoltage": 32,
        "maxcurrent": 5
      }
    }
  }
}

When $MODEL is set to RS_HMPXXXX, I get this error

(labRemote) [pixdaq@itkpix-daq-05 ~]$ python ps.py 
[ERROR]   : Unknown power supply: ROHDE&SCHWARZ,HMP2020,101608,HW50010003/SW2.62
Traceback (most recent call last):
  File "ps.py", line 8, in <module>
    PS = hw.getPowerSupplyChannel('high-current')
RuntimeError: Unknown power supply: ROHDE&SCHWARZ,HMP2020,101608,HW50010003/SW2.62

so on @eressegu 's suggestion, I switch to SCPIPs and it works fine (skipping the check). Why is the check needed? Is there a way to get it to work from python? The PowerSupplyRegistry is not exposed (is that on purpose)?

Additionally, how do I determine the right communication protocol to use? There's no distinct keywords to distinguish between the ones implemented in labRemote. I just scan through all possibilities until one works... but this certainly can't be appropriate?