openapi: 3.1.3
info:
  title: Spiceflow Documentation
  description: Development documentation
  version: 0.0.0
servers:
  - url: https://api.com
paths:
  /openapi:
    get:
      responses:
        '200':
          description: ''
        default:
          description: ''

---
Let's break down what we need to add:

1. We need to add a new method to the `ExampleClientAsync` class for the GET /openapi route
2. The method should be async and use the existing fetch method
3. The route has no parameters or request body
4. The response is untyped in the OpenAPI spec, so we'll return Any
5. We'll add proper type hints and documentation

Here's the code to add:

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

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

    # GET /openapi
    # tags: 
    async def get_openapi(self) -> Any:
        """Fetch OpenAPI specification
        
        Returns:
            Any: The OpenAPI specification document
        """
        response = await self.fetch(
            method="GET",
            path="/openapi"
        )
        
        if response.status != 200:
            raise ExampleError(
                error=f"Failed to fetch OpenAPI specification: {response.status}",
                status=response.status,
                data=await response.text()
            )
            
        return await response.json()

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

The method is added to the existing `ExampleClientAsync` class and follows all the requirements:
- Uses async/await
- Includes type hints
- Handles error cases
- Uses the existing fetch method
- Includes proper documentation
- Returns the parsed JSON response
- Throws ExampleError for non-200 responses