openapi: 3.1.3
info:
  title: Spiceflow Documentation
  description: Development documentation
  version: 0.0.0
servers:
  - url: https://api.com
paths:
  /upload:
    post:
      responses:
        '200':
          description: ''
        default:
          description: ''
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                file:
                  type: string
                  contentEncoding: base64
              required:
                - file
              additionalProperties: false

---
Let's break this down step by step:

1. The route is POST /upload with multipart/form-data content type
2. The request requires a base64 encoded file in the body
3. We need to handle file uploads using aiohttp's multipart form data capabilities
4. We'll need to modify the headers to use multipart/form-data instead of application/json
5. We'll add a new method to the ExampleClientAsync class

Here's the implementation:

```python:client.py
# ... existing code ...

class ExampleClientAsync:
    # ... existing code ...

    # POST /upload
    # Tags: (none)
    async def upload_file(self, file_content: str) -> Any:
        """
        Upload a base64 encoded file
        
        Args:
            file_content: Base64 encoded file content as string
            
        Returns:
            Response from the server
            
        Raises:
            ExampleError: If the request fails
        """
        data = aiohttp.FormData()
        data.add_field('file', file_content)
        
        response = await self.fetch(
            method="POST",
            path="/upload",
            body=None,
            headers={"Content-Type": "multipart/form-data"},
            form_data=data
        )
        
        if response.status != 200:
            error_data = await response.json() if response.content_type == "application/json" else await response.text()
            raise ExampleError(
                f"Upload failed with status {response.status}",
                status=response.status,
                data=error_data
            )
            
        return await response.json() if response.content_type == "application/json" else await response.text()

    async def fetch(
        self,
        method: str,
        path: str,
        query: Optional[Dict[str, Union[str, int, bool, None]]] = None,
        body: Any = None,
        headers: Optional[Dict[str, str]] = None,
        form_data: Optional[aiohttp.FormData] = None,
    ) -> Any:
        url = urllib.parse.urljoin(self.base_url, path)

        if query:
            params = []
            for key, value in query.items():
                if value is not None:
                    params.append(f"{key}={urllib.parse.quote(str(value))}")
            if params:
                url = f"{url}?{'&'.join(params)}"

        request_headers = {}
        if self.token:
            request_headers["Authorization"] = f"Bearer {self.token}"
        if headers:
            request_headers.update(headers)

        async with aiohttp.ClientSession() as session:
            async with session.request(
                method=method,
                url=url,
                headers=request_headers,
                json=body if body is not None else None,
                data=form_data if form_data is not None else None,
            ) as response:
                return response

# ... existing code ...
```