SFTTrainer Data collators

Beginners
1

I have a task in which I am using SFTTrainer for and I want to test performance using different data collators. I have a couple of questions:

  1. What is the default data collator used by SFTTrainer when not using collator parameter.
  2. I found in the documentation that DataCollatorForCompletionsOnly compute loss on response only, how I make sure if the other collators do the same.