* @since 20.0 (present with return type {@link Iterator} since 2.0)
     */
    @Override
    public abstract UnmodifiableIterator<E> iterator();
  }

  /**
   * Returns an unmodifiable <b>view</b> of the union of two sets. The returned set contains all
   * elements that are contained in either backing set. Iterating over the returned set iterates

	if wantFormat := h.Format; wantFormat != FormatUnknown {
		if wantFormat.has(FormatPAX) && !preferPAX {
			wantFormat.mayBe(FormatUSTAR) // PAX implies USTAR allowed too
		}
		format.mayOnlyBe(wantFormat) // Set union of formats allowed and format wanted
	}
	if format == FormatUnknown {
		switch h.Format {
		case FormatUSTAR:
			err = headerError{"Format specifies USTAR", whyNoUSTAR, whyOnlyPAX, whyOnlyGNU}
		case FormatPAX:

      "Licensor" shall mean the copyright owner or entity authorized by
      the copyright owner that is granting the License.

      "Legal Entity" shall mean the union of the acting entity and all
      other entities that control, are controlled by, or are under common
      control with that entity. For the purposes of this definition,

```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"),

* 빈 파일 `__init__.py`을 생성합니다.
* 다음과 같은 `main.py`을 생성합니다:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

### 도커파일

  // Equality 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:
  //   - 'set': `X + Y` performs a union where the array positions of all elements in `X` are preserved and
  //     non-intersecting elements in `Y` are appended, retaining their partial order.

40.792472839355469 -74.005729675292969 40.745033264160156 1 6.46 23.5 0 0.5 0 0 24 2 1 75 68 green 0.04 0.0 0.0 62 37 5.37 1267 168 1 Manhattan 016800 1016800 E MN33 East Harlem South 3804 12 89 1 Manhattan 008900 1008900 I MN13 Hudson Yards-Chelsea-Flatiron-Union Square 3807 3389240 2 2014-03-10 18:19:09 2014-03-10 18:26:44 N 1 -73.950828552246094 40.791755676269531 -73.961746215820312 40.800731658935547 1 1.25 7 1 0.5 0 0 8.5 2 1 75 24 green 0.00 1.2 0.0 51 36 5.37 1267 168 1 Manhattan 016800 1016800 E MN33...

		for _, p := range policiesToUpdate.ToSlice() {
			if _, found := cache.iamPolicyDocsMap[p]; !found {
				err = errNoSuchPolicy
				return
			}
		}
		newPolicySet = existingPolicySet.Union(policiesToUpdate)
	} else {
		// policies to detach => inputPolicies ∩ existing (intersection)
		policiesToUpdate = policiesToUpdate.Intersection(existingPolicySet)

	list := make([]string, 0, n)
	for i := 0; i < n; i++ {
		emb := typ.EmbeddedType(i)
		switch emb := emb.(type) {
		case *types.Interface:
			list = append(list, w.sortedEmbeddeds(emb)...)
		case *types.Union:
			var buf bytes.Buffer
			nu := emb.Len()
			for i := 0; i < nu; i++ {
				if i > 0 {
					buf.WriteString(" | ")
				}
				term := emb.Term(i)
				if term.Tilde() {
					buf.WriteByte('~')

  // +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