```Python
from typing import Union
from fastapi import Cookie, FastAPI, Header, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
def main(
    item_id: int = Path(gt=0),
    query: Union[str, None] = Query(default=None, max_length=10),
    session: Union[str, None] = Cookie(default=None, min_length=3),
    x_trace: Union[str, None] = Header(default=None, title="Tracing header"),

  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // The set of all endpoints is the union of all subsets. Addresses are placed into
  // subsets according to the IPs they share. A single address with multiple ports,
  // some of which are ready and some of which are not (because they come from

interface {
	~[]byte  // the underlying type of []byte is itself
	~MyInt   // illegal: the underlying type of MyInt is not MyInt
	~error   // illegal: error is an interface
}
</pre>

<p>
Union elements denote unions of type sets:
</p>

<pre>
// The Float interface represents all floating-point types
// (including any named types whose underlying types are
// either float32 or float64).

* Add support for the webhook authorizer to make a Deny decision that short-circuits the union authorizer and immediately returns Deny.  ([#53273](https://github.com/kubernetes/kubernetes/pull/53273), [@mikedanese](https://github.com/mikedanese))