expand docstring (#1273)

megatron/text_generation_utils.py

@@ -91,6 +91,8 @@ def filter_logits(logits, top_k=0, top_p=0.0, filter_value=-float("Inf")):
     This function has been mostly taken from huggingface conversational ai code at
     https://medium.com/huggingface/how-to-build-a-state-of-the-art-conversational-ai-with-transfer-learning-2d818ac26313
 
+    When both top_k and top_p are specified, tokens are first filtered according to top_k, renormalized, and then filtered according to top_p.
+
     logits: torch.Tensor -> logits of megatron model.
     top_k: integer -> integer between 0 and the models vocab size. Filters out any logits with a probability less than that of the top_kth token.
     top_p: float -> Top-p (nucleus) sampling chooses from the smallest possible set of tokens whose cumulative probability exceeds the probability top_p.