update pydantic blog

_drafts/2024-02-18-pydantic.md

@@ -289,6 +289,32 @@ mod = wrapper.visit(command)
 print(mod.code)
 ```
 
+## pydantic 的更多使用例子
+
+### 例子 1: A 属性的值由 B 属性确定
+
+```python
+from pydantic.v1 import BaseModel, root_validator
+from typing import List, Dict, Any
+
+class A(BaseModel):
+    embedding_functions: Dict[str, Any]
+    vector_names: List[str]
+
+    @root_validator(pre=True)
+    def add_vector_names(cls, values):
+        values["vector_names"] = list(values["embedding_functions"].keys())
+        return values
+
+    @classmethod
+    def from_functions(cls, embedding_functions): 
+        return cls(embedding_functions=embedding_functions)
+
+embedding_functions = {"a": lambda x: [1]}
+a = A.from_functions(embedding_functions)
+a = A(embedding_functions=embedding_functions)
+```
+
 ## FastAPI
 
 - path parameter: 可以使用 `fastapi.Path` 配合 `typing.Annotated` 来做 type hint 以及数据校验