It’s likely a ventless (condensing) dryer. I had an all-in-one washer/dryer that used this type of drying. My understanding is that it is essentially a really strong dehumidifier, it heats up slightly to aid the process but doesn’t get hot like a conventional vented dryer. My all-in-one pumped the condensate out through the washer drain line, if it has a compartment that needs to be emptied it probably doesn’t have a pump.