Add docstring for dspy.ReAct (#8334)

* Add docstring for dspy.ReAct

* improve docstring

* fix type hint

* Update react.py

* Update react.py

---------

Co-authored-by: Omar Khattab <okhat@users.noreply.github.com>

Author: chenmoneygithub

dspy/predict/react.py

@@ -1,5 +1,5 @@
 import logging
-from typing import Any, Callable, Literal
+from typing import TYPE_CHECKING, Any, Callable, Literal, Type
 
 from litellm import ContextWindowExceededError
 
@@ -10,11 +10,33 @@
 
 logger = logging.getLogger(__name__)
 
+if TYPE_CHECKING:
+    from dspy.signatures.signature import Signature
+
 
 class ReAct(Module):
-    def __init__(self, signature, tools: list[Callable], max_iters=5):
+    def __init__(self, signature: Type["Signature"], tools: list[Callable], max_iters: int = 10):
         """
-        `tools` is either a list of functions, callable classes, or `dspy.Tool` instances.
+        ReAct stands for "Reasoning and Acting," a popular paradigm for building tool-using agents.
+        In this approach, the language model is iteratively provided with a list of tools and has
+        to reason about the current situation. The model decides whether to call a tool to gather more
+        information or to finish the task based on its reasoning process. The DSPy version of ReAct is
+        generalized to work over any signature, thanks to signature polymorphism.
+
+        Args:
+            signature: The signature of the module, which defines the input and output of the react module.
+            tools (list[Callable]): A list of functions, callable objects, or `dspy.Tool` instances.
+            max_iters (Optional[int]): The maximum number of iterations to run. Defaults to 10.
+
+        Example:
+
+        ```python
+        def get_weather(city: str) -> str:
+            return f"The weather in {city} is sunny."
+
+        react = dspy.ReAct(signature="question->answer", tools=[get_weather])
+        pred = react(question="What is the weather in Tokyo?")
+        ```
         """
         super().__init__()
         self.signature = signature = ensure_signature(signature)