{!> ../../docs_src/body_nested_models/tutorial002.py!}
```

////

## Set types

But then we think about it, and realize that tags shouldn't repeat, they would probably be unique strings.

And Python has a special data type for sets of unique items, the `set`.

Then we can declare `tags` as a set of strings:

//// tab | Python 3.10+

```Python hl_lines="12"
{!> ../../docs_src/body_nested_models/tutorial003_py310.py!}

import org.w3c.dom.Node;

public class PrunedTag {
    private final String tag;
    private String id;
    private String css;
    private String attrName;
    private String attrValue;

    public PrunedTag(final String tag) {
        this.tag = tag;
    }

    public boolean matches(final Node node) {
        if (tag.equalsIgnoreCase(node.getNodeName())) {
            if (attrName != null) {

        private final HttpServletRequest request;

        private final String[] tags;

        protected RequestParameter(final HttpServletRequest request, final String query, final String[] tags, final String[] fields,
                final int num) {
            this.query = query;
            this.tags = tags;
            this.fields = fields;
            this.num = num;
            this.request = request;

<?xml version="1.0" encoding="UTF-8"?>
<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/">
  <ShortName>Fess</ShortName>
  <Description>Full Text Search for Your Documents.</Description>
  <Tags>Full Text Search</Tags>
  <Contact>******@****.***</Contact>
  <SearchForm>http://localhost:8080/fess/</SearchForm>
  <Url type="text/html" template="http://localhost:8080/fess/search?q={searchTerms}"/>
  <InputEncoding>UTF-8</InputEncoding>

from fastapi import FastAPI, status
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: set[str] = set()


@app.post("/items/", response_model=Item, status_code=status.HTTP_201_CREATED)
async def create_item(item: Item):

    name: str
    description: str | None = None
    price: float
    tax: float = 10.5
    tags: list[str] = []


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The bartenders", "price": 62, "tax": 20.2},
    "baz": {"name": "Baz", "description": None, "price": 50.2, "tax": 10.5, "tags": []},
}


@app.get("/items/{item_id}", response_model=Item, response_model_exclude_unset=True)

file_path = Path("./openapi.json")
openapi_content = json.loads(file_path.read_text())

for path_data in openapi_content["paths"].values():
    for operation in path_data.values():
        tag = operation["tags"][0]
        operation_id = operation["operationId"]
        to_remove = f"{tag}-"
        new_operation_id = operation_id[len(to_remove) :]
        operation["operationId"] = new_operation_id

from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: Union[str, None] = None
    price: float
    tax: Union[float, None] = None
    tags: set[str] = set()


@app.post("/items/", response_model=Item, status_code=status.HTTP_201_CREATED)
async def create_item(item: Item):

        <item sex="male" custid="A12345">
                <name>鈴木太郎</name>
                <access kind="email"></access>
                <access kind="url">http://www.taro.com/</access>
                <image file="taro.png" />
        </item>
        <item sex="male" custid="B23456">
                <name>佐藤二朗</name>
                <access kind="email">******@****.***</access>

class FilterParams(BaseModel):
    model_config = {"extra": "forbid"}

    limit: int = Field(100, gt=0, le=100)
    offset: int = Field(0, ge=0)
    order_by: Literal["created_at", "updated_at"] = "created_at"
    tags: list[str] = []


@app.get("/items/")
async def read_items(filter_query: Annotated[FilterParams, Query()]):