I have the following setup:

class Response(BaseModel):
  stuff1: int | None
  stuff2: str
  metadata: Metadata
 
class Metadata(BaseModel):
  attr1: str
  attr2: int | None = None

When Response is serialized/dumped as a JSON, I want attr2 to be included only if it is non-null. Importantly, stuff1 should be included regardless of its type (null or int). The exclude_none parameter to model.model_dump would apply to all entries of response, so it is not suitable.

I know this feature is part of Pydantic 2.x but I am using 1.10.

desired dump result when response.metadata.attr2 = None

response = {
  "stuff1": None
  "stuff2": 4
  "metadata": {
    "attr1": "hello"
}