adding key pair dataset (#19765)

docs/source/en/main_classes/pipelines.mdx

@@ -91,7 +91,7 @@ pipe = pipeline("automatic-speech-recognition", model="facebook/wav2vec2-base-96
 dataset = datasets.load_dataset("superb", name="asr", split="test")
 
 # KeyDataset (only *pt*) will simply return the item in the dict returned by the dataset item
-# as we're not interested in the *target* part of the dataset.
+# as we're not interested in the *target* part of the dataset. For sentence pair use KeyPairDataset
 for out in tqdm(pipe(KeyDataset(dataset, "file"))):
     print(out)
     # {"text": "NUMBER TEN FRESH NELLY IS WAITING ON YOU GOOD NIGHT HUSBAND"}