Fix mamba integration by making it a variant of outlines.models.trans…

…formers

docs/reference/models/transformers.md

@@ -82,3 +82,62 @@ print(output)
 ```
 
 [transformers]: https://github.com/huggingface/transformers
+
+
+# Alternative Model Classes
+
+`outlines.models.transformers` defaults to `transformers.AutoModelForCausalLM`, which is the appropriate class for most standard large language models, including Llama 3, Mistral, Phi-3, etc.
+
+However other variants with unique behavior can be used as well by passing the appropriate class.
+
+### Mamba
+
+[Mamba](https://github.com/state-spaces/mamba) is a transformers alternative which employs memory efficient, linear-time decoding.
+
+To use Mamba with outlines you must first install the necessary requirements:
+```
+pip install causal-conv1d>=1.2.0 mamba-ssm torch transformers
+```
+
+Then you can either create an Mamba-2 Outlines model via
+```
+import outlines
+
+model = outlines.models.mamba("state-spaces/mamba-2.8b-hf")
+```
+
+or explicitly with
+```
+import outlines
+from transformers import MambaForCausalLM
+
+model = outlines.models.transformers(
+    "state-spaces/mamba-2.8b-hf",
+    model_class=MambaForCausalLM
+)
+```
+
+Further Reading:
+- https://huggingface.co/docs/transformers/en/model_doc/mamba
+
+### Encoder-Decoder Models
+
+You can use encoder-decoder (seq2seq) models like T5 and BERT with Outlines.
+
+Be cautious with model selection though, some models such as `t5-base` don't include certain characters (`{`) and you may get an error when trying to perform structured generation.
+
+Example:
+```
+import outlines
+from transformers import AutoModelForSeq2SeqLM
+
+model = models.transformers(
+    model_name="EleutherAI/pile-t5-large",
+    model_class=transformers.AutoModelForSeq2SeqLM,
+)
+```
+
+
+### Multi-Modal Models
+
+/Coming soon/

outlines/models/__init__.py

@@ -9,10 +9,9 @@
 
 from .exllamav2 import ExLlamaV2Model, exl2
 from .llamacpp import LlamaCpp, llamacpp
-from .mamba import Mamba, mamba
 from .mlxlm import MLXLM, mlxlm
 from .openai import OpenAI, azure_openai, openai
-from .transformers import Transformers, TransformerTokenizer, transformers
+from .transformers import Transformers, TransformerTokenizer, transformers, mamba
 from .vllm import VLLM, vllm
 
-LogitsGenerator = Union[Transformers, LlamaCpp, ExLlamaV2Model, Mamba]
+LogitsGenerator = Union[Transformers, LlamaCpp, ExLlamaV2Model]

outlines/models/transformers.py

@@ -369,6 +369,8 @@ def transformers(
     device: Optional[str] = None,
     model_kwargs: dict = {},
     tokenizer_kwargs: dict = {},
+    model_class=None,
+    tokenizer_class=None,
 ):
     """Instantiate a model from the `transformers` library and its tokenizer.
 
@@ -391,19 +393,47 @@ def transformers(
     A `TransformersModel` model instance.
 
     """
-    try:
-        from transformers import AutoModelForCausalLM, AutoTokenizer
-    except ImportError:
-        raise ImportError(
-            "The `transformers` library needs to be installed in order to use `transformers` models."
-        )
+    if model_class is None or tokenizer_class is None:
+        try:
+            from transformers import AutoModelForCausalLM, AutoTokenizer
+        except ImportError:
+            raise ImportError(
+                "The `transformers` library needs to be installed in order to use `transformers` models."
+            )
+    if model_class is None:
+        model_class = AutoModelForCausalLM
+    if tokenizer_class is None:
+        tokenizer_class = AutoTokenizer
 
     if device is not None:
         model_kwargs["device_map"] = device
 
-    model = AutoModelForCausalLM.from_pretrained(model_name, **model_kwargs)
+    model = model_class.from_pretrained(model_name, **model_kwargs)
 
     tokenizer_kwargs.setdefault("padding_side", "left")
-    tokenizer = AutoTokenizer.from_pretrained(model_name, **tokenizer_kwargs)
+    tokenizer = tokenizer_class.from_pretrained(model_name, **tokenizer_kwargs)
 
     return Transformers(model, tokenizer)
+
+
+def mamba(
+    model_name: str,
+    device: Optional[str] = None,
+    model_kwargs: dict = {},
+    tokenizer_kwargs: dict = {},
+):
+    try:
+        from transformers import MambaForCausalLM
+
+    except ImportError:
+        raise ImportError(
+            "The `mamba_ssm`, `torch` and `transformer` libraries needs to be installed in order to use Mamba people."
+        )
+
+    return transformers(
+        model_name=model_name,
+        device=device,
+        model_kwargs=model_kwargs,
+        tokenizer_kwargs=tokenizer_kwargs,
+        model_class=MambaForCausalLM,
+    )

tests/generate/test_generate.py

@@ -31,24 +31,28 @@ def model_vllm(tmp_path_factory):
     return models.vllm("facebook/opt-125m")
 
 
-# TODO: mamba / exllamav2 failing in main, address in https://github.com/outlines-dev/outlines/issues/808
-"""
 @pytest.fixture(scope="session")
-def model_exllamav2(tmp_path_factory):
-    return models.exllamav2(
-        model_path="blockblockblock/TinyLlama-1.1B-Chat-v1.0-bpw4-exl2",
-        device="cpu"
+def model_mamba(tmp_path_factory):
+    return models.mamba(model_name="state-spaces/mamba-130m-hf", device="cpu")
+
+
+@pytest.fixture(scope="session")
+def model_t5(tmp_path_factory):
+    from transformers import T5ForConditionalGeneration
+
+    return models.transformers(
+        "google/t5-efficient-mini", device="cpu", model_class=T5ForConditionalGeneration
     )
 
 
+# TODO: exllamav2 failing in main, address in https://github.com/outlines-dev/outlines/issues/808
+"""
 @pytest.fixture(scope="session")
-def model_mamba(tmp_path_factory):
-    return models.mamba(
-        model_name="state-spaces/mamba-130m-hf",
+def model_exllamav2(tmp_path_factory):
+    return models.exllamav2(
+        model_path="blockblockblock/TinyLlama-1.1B-Chat-v1.0-bpw4-exl2",
         device="cpu"
     )
-
-ALL_MODEL_FIXTURES = ("model_llamacpp", "model_mlxlm", "model_transformers", "model_vllm", "model_exllamav2", "model_mamba")
 """
 
 
@@ -57,6 +61,8 @@ def model_mamba(tmp_path_factory):
     "model_mlxlm",
     "model_transformers",
     "model_vllm",
+    "model_mamba",
+    "model_t5",
 )