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2104cf0d9a
This PR addresses deprecation warnings users encounter when using
LangChain tools with Pydantic v2:
```
PydanticDeprecatedSince20: The `schema` method is deprecated; use `model_json_schema` instead.
Deprecated in Pydantic V2.0 to be removed in V3.0.
```
## Root Cause
Several LangChain components were still using the deprecated `.schema()`
method directly instead of the Pydantic v1/v2 compatible approach. While
users calling `.schema()` on returned models will still see warnings
(which is correct), LangChain's internal code should not generate these
warnings.
## Changes Made
Updated 3 files to use the standard compatibility pattern:
```python
# Before (deprecated)
schema = model.schema()
# After (compatible with both v1 and v2)
if hasattr(model, "model_json_schema"):
schema = model.model_json_schema() # Pydantic v2
else:
schema = model.schema() # Pydantic v1
```
### Files Updated:
- **`evaluation/parsing/json_schema.py`**: Fixed `_parse_json()` method
to handle Pydantic models correctly
- **`output_parsers/yaml.py`**: Fixed `get_format_instructions()` to use
compatible schema access
- **`chains/openai_functions/citation_fuzzy_match.py`**: Fixed direct
`.schema()` call on QuestionAnswer model
## Verification
✅ **Zero breaking changes** - all existing functionality preserved
✅ **No deprecation warnings** from LangChain internal code
✅ **Backward compatible** with Pydantic v1
✅ **Forward compatible** with Pydantic v2
✅ **Edge cases handled** (strings, plain objects, etc.)
## User Impact
LangChain users will no longer see deprecation warnings from internal
LangChain code. Users who directly call `.schema()` on schemas returned
by LangChain should adopt the same compatibility pattern:
```python
# User code should use this pattern
input_schema = tool.get_input_schema()
if hasattr(input_schema, "model_json_schema"):
schema_result = input_schema.model_json_schema()
else:
schema_result = input_schema.schema()
```
Fixes #31458.
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