add example generation + peft

docs/source/en/model_doc/mamba.md

@@ -37,6 +37,60 @@ Tips:
 This model was contributed by [ArthurZ](https://huggingface.co/ArthurZ).
 The original code can be found [here](https://github.com/state-spaces/mamba).
 
+# Usage
+
+### A simple generation example: 
+```python 
+from transformers import MambaConfig, MambaForCausalLM, AutoTokenizer
+import torch
+
+tokenizer = AutoTokenizer.from_pretrained("ArthurZ/mamba-130m")
+tokenizer.pad_token = tokenizer.eos_token
+
+model = MambaForCausalLM.from_pretrained("ArthurZ/mamba-130m", vocab_size=50280, num_hidden_layers=24, torch_dtype=torch.float32)
+model.config.use_cache = True
+input_ids = tokenizer("Hey how are you doing?", return_tensors= "pt")["input_ids"]
+
+out = model.generate(input_ids, max_new_tokens=10)
+print(tokenizer.batch_decode(out))
+```
+
+### Peft finetuning
+The slow version is not very stable for training, and the fast one needs `float32`!
+
+```python 
+from datasets import load_dataset
+from trl import SFTTrainer
+from peft import LoraConfig
+from transformers import AutoTokenizer, AutoModelForCausalLM, TrainingArguments
+model_id = "ArthurZ/mamba-2.8b"
+tokenizer = AutoTokenizer.from_pretrained(model_id, pad_token ="<s>")
+model = AutoModelForCausalLM.from_pretrained(model_id)
+dataset = load_dataset("Abirate/english_quotes", split="train")
+training_args = TrainingArguments(
+    output_dir="./results",
+    num_train_epochs=3,
+    per_device_train_batch_size=4,
+    logging_dir='./logs',
+    logging_steps=10,
+    learning_rate=2e-3
+)
+lora_config =  LoraConfig(
+        r=8,
+        target_modules="all-linear",
+        task_type="CAUSAL_LM",
+        bias="none"
+)
+trainer = SFTTrainer(
+    model=model,
+    tokenizer=tokenizer,
+    args=training_args,
+    peft_config=lora_config,
+    train_dataset=dataset,
+    dataset_text_field="quote",
+)
+trainer.train()
+```
 
 ## MambaConfig