fix #841, the issue with the api documentation.

docs/api/modules/ChainOfThought.md

@@ -13,23 +13,20 @@ class ChainOfThought(Predict):
 
         self.activated = activated
 
-        signature = self.signature
-        *keys, last_key = signature.kwargs.keys()
-
-        DEFAULT_RATIONALE_TYPE = dsp.Type(prefix="Reasoning: Let's think step by step in order to",
-                                          desc="${produce the " + last_key + "}. We ...")
-
-        rationale_type = rationale_type or DEFAULT_RATIONALE_TYPE
-
-        extended_kwargs = {key: signature.kwargs[key] for key in keys}
-        extended_kwargs.update({'rationale': rationale_type, last_key: signature.kwargs[last_key]})
-
-        self.extended_signature = dsp.Template(signature.instructions, **extended_kwargs)
+        signature = ensure_signature(self.signature)
+        *_keys, last_key = signature.output_fields.keys()
+
+        rationale_type = rationale_type or dspy.OutputField(
+            prefix="Reasoning: Let's think step by step in order to",
+            desc="${produce the " + last_key + "}. We ...",
+        )
+
+        self.extended_signature = signature.prepend("rationale", rationale_type, type_=str)
 ```
 
 **Parameters:**
 - `signature` (_Any_): Signature of predictive model.
-- `rationale_type` (_dsp.Type_, _optional_): Rationale type for reasoning steps. Defaults to `None`.
+- `rationale_type` (_dspy.OutputField_, _optional_): Rationale type for reasoning steps. Defaults to `None`.
 - `activated` (_bool_, _optional_): Flag for activated chain of thought processing. Defaults to `True`.
 - `**config` (_dict_): Additional configuration parameters for model.
 
@@ -64,3 +61,15 @@ pred = generate_answer(question=question)
 print(f"Question: {question}")
 print(f"Predicted Answer: {pred.answer}")
 ```
+
+The following example shows how to specify your custom rationale. Here `answer` corresponds to the last key to produce, it may be different in your case. 
+
+```python
+#define a custom rationale
+rationale_type = dspy.OutputField(
+            prefix="Reasoning: Let's think step by step in order to",
+            desc="${produce the answer}. We ...",
+        )
+#Pass signature to ChainOfThought module
+generate_answer = dspy.ChainOfThought(BasicQA, rationale_type=rationale_type)
+```

docs/api/modules/ChainOfThoughtWithHint.md

@@ -8,32 +8,23 @@ The constructor initializes the `ChainOfThoughtWithHint` class and sets up its a
 class ChainOfThoughtWithHint(Predict):
     def __init__(self, signature, rationale_type=None, activated=True, **config):
         super().__init__(signature, **config)
-
         self.activated = activated
-
         signature = self.signature
-        *keys, last_key = signature.kwargs.keys()
-
-        DEFAULT_HINT_TYPE = dsp.Type(prefix="Hint:", desc="${hint}")
-
-        DEFAULT_RATIONALE_TYPE = dsp.Type(prefix="Reasoning: Let's think step by step in order to",
-                                          desc="${produce the " + last_key + "}. We ...")
 
-        rationale_type = rationale_type or DEFAULT_RATIONALE_TYPE
-
-        extended_kwargs1 = {key: signature.kwargs[key] for key in keys}
-        extended_kwargs1.update({'rationale': rationale_type, last_key: signature.kwargs[last_key]})
+        *keys, last_key = signature.fields.keys()
+        rationale_type = rationale_type or dspy.OutputField(
+            prefix="Reasoning: Let's think step by step in order to",
+            desc="${produce the " + last_key + "}. We ...",
+        )
+        self.extended_signature1 = self.signature.insert(-2, "rationale", rationale_type, type_=str)
 
-        extended_kwargs2 = {key: signature.kwargs[key] for key in keys}
-        extended_kwargs2.update({'hint': DEFAULT_HINT_TYPE, 'rationale': rationale_type, last_key: signature.kwargs[last_key]})
-
-        self.extended_signature1 = dsp.Template(signature.instructions, **extended_kwargs1)
-        self.extended_signature2 = dsp.Template(signature.instructions, **extended_kwargs2)
+        DEFAULT_HINT_TYPE = dspy.OutputField()
+        self.extended_signature2 = self.extended_signature1.insert(-2, "hint", DEFAULT_HINT_TYPE, type_=str)
 ```
 
 **Parameters:**
 - `signature` (_Any_): Signature of predictive model.
-- `rationale_type` (_dsp.Type_, _optional_): Rationale type for reasoning steps. Defaults to `None`.
+- `rationale_type` (_dspy.OutputField_, _optional_): Rationale type for reasoning steps. Defaults to `None`.
 - `activated` (_bool_, _optional_): Flag for activated chain of thought processing. Defaults to `True`.
 - `**config` (_dict_): Additional configuration parameters for model.