# ❌ No
# collator.py
class TRLCollator: ...

# dpo_trainer.py
class DPOTrainer:
    def __init__(self, ...):
        self.collator = TRLCollator(...)

# kto_trainer.py
class KTOTrainer:
    def __init__(self, ...):
        self.collator = TRLCollator(...)

# ✅ Better
# dpo_trainer.py
class DataCollatorForPreference: ...

class DPOTrainer:
    def __init__(self, ...):
        self.collator = DataCollatorForPreference(...)

# kto_trainer.py
class DataCollatorForUnpairedPreference: ...

class KTOTrainer:
    def __init__(self, ...):
        self.collator = DataCollatorForUnpairedPreference(...)