Update the documentation for the Gemini integration

docs/reference/models/gemini.md

@@ -0,0 +1,88 @@
+# Gemini
+
+!!! Installation
+
+    You need to install the `google-generativeai` library to be able to use the Gemini API in Outlines. Or alternatively you can run:
+
+    ```bash
+    pip install "outlines[gemini]"
+    ```
+
+## Gemini models
+
+Outlines supports models available via the Gemini API, e.g. Gemini 1.5. You can initialize the model by passing the model name to `outlines.models.Gemini`:
+
+```python
+from outlines import models
+
+model = models.Gemini("gemini-1-5-flash")
+model = models.Gemini("gemini-1-5-pro")
+```
+
+Check the [Gemini documentation](https://ai.google.dev/gemini-api/docs/models/gemini) for an up-to-date list of available models.
+
+## Text generation
+
+To generate text using a Gemini model you need to build a `Generator` object, possibly with the desired output type. You can then call the model by calling the `Generator`. The method accepts every argument that you could pass to the `client.completions.create` function, as keyword arguments:
+
+```python
+from outlines import models, Generator
+
+model = models.Gemini("gemini-1-5-flash")
+generator = Generator(model)
+result = generator("Prompt", max_tokens=1024)
+```
+
+### Structured generation
+
+Gemini provides support for structured outputs.
+
+#### Json Schema
+
+Outlines provides support for JSON Schema-based structured generation with the Gemini models:
+
+```python
+from collections import TypedDict
+from outlines import Generator, models
+from outlines.types import Json
+
+model = models.Gemini("gemini-1-5-flash")
+
+class Person(TypedDict):
+    first_name: str
+    last_name: str
+    age: int
+
+generator = Generator(model, Json(Person))
+generator("current indian prime minister on january 1st 2023")
+# Person(first_name='Narendra', last_name='Modi', age=72)
+```
+
+Because of the current limitations of the Gemini SDK only The following objects can be used to define the structure of the Json object:
+- A Pydantic model
+- A TypedDict
+
+#### Multiple choices
+
+Outlines provides support for multiple-choices structured generation. Enums and lists of choices are supported:
+
+```python
+from enum import Enum
+from outlines import Generator, models
+from outlines.types import Choice
+
+model = models.Gemini("gemini-1-5-flash")
+
+class Foo(Enum):
+    foo = "Foo"
+    fizz = "Fizz"
+    fuzz = "Fuzz"
+
+generator = Generator(model, Choice(Foo))
+generator("current indian prime minister on january 1st 2023")
+# Person(first_name='Narendra', last_name='Modi', age=72)
+```
+
+The following objects can be used to define the choices:
+- An Enum object
+- A Python list

pyproject.toml

@@ -50,6 +50,7 @@ vllm = ["vllm", "transformers", "numpy2"]
 transformers = ["transformers", "accelerate", "datasets", "numpy<2"]
 mlxlm = ["mlx-lm", "datasets"]
 openai = ["openai"]
+gemini = ["google-generativeai"]
 llamacpp = ["llama-cpp-python", "transformers", "datasets", "numpy<2"]
 exllamav2 = ["exllamav2"]
 test = [