```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"),

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).

	// parameters such as nameservers and search paths should be defined via
	// DNSConfig.
	DNSNone DNSPolicy = "None"
)

// NodeSelector represents the union of the results of one or more label queries
// over a set of nodes; that is, it represents the OR of the selectors represented
// by the node selector terms.
type NodeSelector struct {

  // +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

  // +optional
  optional PodAntiAffinity podAntiAffinity = 3;
}

// AppArmorProfile defines a pod or container's AppArmor settings.
// +union
message AppArmorProfile {
  // type indicates which kind of AppArmor profile will be applied.
  // Valid options are:
  //   Localhost - a profile pre-loaded on the node.

const (
	// DefaultTerminationGracePeriodSeconds indicates the default duration in
	// seconds a pod needs to terminate gracefully.
	DefaultTerminationGracePeriodSeconds = 30
)

// A node selector represents the union of the results of one or more label queries
// over a set of nodes; that is, it represents the OR of the selectors represented
// by the node selector terms.
// +structType=atomic
type NodeSelector struct {

	"metadata": "Standard object's metadata. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata",

            "type": "string"
          }
        },
        "required": [
          "type"
        ],
        "type": "object",
        "x-kubernetes-unions": [
          {
            "discriminator": "type",
            "fields-to-discriminateBy": {
              "localhostProfile": "LocalhostProfile"
            }
          }
        ]
      },

\"object.redact__underscores__d > 0\"}\n\nEquality on arrays with list type of 'set' or 'map' ignores element order, i.e. [1, 2] == [2, 1]. Concatenation on arrays with x-kubernetes-list-type use the semantics of the list type:\n  - 'set': `X + Y` performs a union where the array positions of all elements in `X` are preserved and\n    non-intersecting elements in `Y` are appended, retaining their partial order.\n  - 'map': `X + Y` performs a merge where the array positions of all keys in `X` are preserved but...

res__d > 0\"}\n\nEquality on arrays with x-kubernetes-list-type of 'set' or 'map' ignores element order, i.e. [1, 2] == [2, 1]. Concatenation on arrays with x-kubernetes-list-type use the semantics of the list type:\n  - 'set': `X + Y` performs a union where the array positions of all elements in `X` are preserved and\n    non-intersecting elements in `Y` are appended, retaining their partial order.\n  - 'map': `X + Y` performs a merge where the array positions of all keys in `X` are preserved but...