Add example for training with datasets

bindings/python/examples/train_with_datasets.py

@@ -0,0 +1,19 @@
+import datasets
+from tokenizers import normalizers, pre_tokenizers, Tokenizer, models, trainers
+
+# Build a tokenizer
+bpe_tokenizer = Tokenizer(models.BPE())
+bpe_tokenizer.pre_tokenizer = pre_tokenizers.Whitespace()
+bpe_tokenizer.normalizer = normalizers.Lowercase()
+
+# Initialize a dataset
+dataset = datasets.load_dataset("wikitext", "wikitext-103-raw-v1")
+
+# Build an iterator over this dataset
+def batch_iterator():
+    batch_length = 1000
+    for i in range(0, len(dataset["train"]), batch_length):
+        yield dataset["train"][i : i + batch_length]["text"]
+
+# And finally train
+bpe_tokenizer.train_from_iterator(batch_iterator(), length=len(dataset["train"]))