```python
mapping = {
    "delta fan with 151 cfm": "unknown",
    "delta fans": "unknown",
    "delta fans afb1212hhe-4l15 fan": "unknown",
    "delta pfb1212uhe-f00 fans": "unknown",
    "delta pfc1212de fans": "unknown",
    "delta pfc1212de-pwm": "unknown",
    "delta pfr0612uhe fans": "unknown",
    "delta push": "unknown",
    "delta qfr1212ghe": "unknown",
    "delta qfr1212ghe fans": "unknown",
    "delta tfc1212de fan": "unknown",
    "deltas": "unknown",
    "demo rig": "unknown",
    "demo s-5": "unknown", # No exact match, possibly a typo or shorthand for a specific model.
    "denatured alcohol or isopropyl": "unknown",
    "deneb core": "unknown",
    "desk fan": "unknown",
    "desktop": "unknown",
    "desktop fan": "unknown",
    "desktop machine": "unknown",
    "desktop pc": "unknown",
    "desktop style computer case": "unknown",
    "desktops": "unknown",
    "dev unit": "unknown",
    "developer chips": "unknown",
    "development boards": "unknown",
    "device": "unknown",
    "devices for testing purposes": "unknown",
    "df04056b12u": "unknown",
    "dhl": "unknown",
    "dhl truck": "unknown",
    "dhub-h7 power adapters": "unknown",
    "diablo": "unknown",
    "diablo miner": "unknown",
    "diablominer": "unknown",
    "diamond pickaxe": "unknown",
    "die 0 knc mercury": "kncminer mercury", # Closest match based on context, but not an exact match.
    "die 1": "unknown",
    "dielectric grease": "unknown",
    "dies": "unknown",
    "digikey fans": "unknown",
    "digilent microblaze starter kit": "unknown",
    "digilent nexys3 board": "unknown",
    "digital caliper (micrometer)": "unknown",
    "digital innovations 7 port hub": "unknown",
    "digital signing for google play": "unknown",
    "digital timer power switch": "unknown",
    "digitus 7-port hub": "unknown",
    "diode": "unknown",
    "dipo electronic 19 port hubs": "unknown",
}
```