Fix import error from deprecation in transformers (#1415)

* Fix import error from  deprecation in transformers

* Fix import path

trl/core.py

@@ -22,7 +22,7 @@
 import torch.nn as nn
 import torch.nn.functional as F
 from torch.nn.utils.rnn import pad_sequence
-from transformers import top_k_top_p_filtering
+from transformers.generation import TopKLogitsWarper, TopPLogitsWarper
 
 from .import_utils import is_npu_available, is_xpu_available
 
@@ -36,6 +36,42 @@
 WANDB_PADDING = -1
 
 
+def top_k_top_p_filtering(
+    logits: torch.FloatTensor,
+    top_k: int = 0,
+    top_p: float = 1.0,
+    filter_value: float = -float("Inf"),
+    min_tokens_to_keep: int = 1,
+) -> torch.FloatTensor:
+    """
+    Filter a distribution of logits using top-k and/or nucleus (top-p) filtering.
+
+    Args:
+        logits: logits distribution shape (batch size, vocabulary size)
+        top_k (`int`, *optional*, defaults to 0):
+            If > 0, only keep the top k tokens with highest probability (top-k filtering)
+        top_p (`float`, *optional*, defaults to 1.0):
+            If < 1.0, only keep the top tokens with cumulative probability >= top_p (nucleus filtering). Nucleus
+            filtering is described in Holtzman et al. (http://arxiv.org/abs/1904.09751)
+        min_tokens_to_keep (`int`, *optional*, defaults to 1):
+            Minimumber of tokens we keep per batch example in the output.
+
+    From: https://gist.github.com/thomwolf/1a5a29f6962089e871b94cbd09daf317
+    """
+
+    if top_k > 0:
+        logits = TopKLogitsWarper(top_k=top_k, filter_value=filter_value, min_tokens_to_keep=min_tokens_to_keep)(
+            None, logits
+        )
+
+    if 0 <= top_p <= 1.0:
+        logits = TopPLogitsWarper(top_p=top_p, filter_value=filter_value, min_tokens_to_keep=min_tokens_to_keep)(
+            None, logits
+        )
+
+    return logits
+
+
 def flatten_dict(nested: Dict, sep: str = "/") -> Dict:
     """Flatten dictionary and concatenate nested keys with separator."""