</li>
<li>
	At most one of the type parameters has a known type argument.
	In this case, the type parameters are <i>joined</i>:
	they both stand for the same type argument.
	If neither type parameter has a known type argument yet,
	a future type argument inferred for one the type parameters
	is simultaneously inferred for both of them.
</li>
<li>
	Both type parameters have a known type argument

```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"),

    /** The key of the configuration. e.g. UTF-8 */
    String CRAWLER_DOCUMENT_SITE_ENCODING = "crawler.document.site.encoding";

    /** The key of the configuration. e.g. unknown */
    String CRAWLER_DOCUMENT_UNKNOWN_HOSTNAME = "crawler.document.unknown.hostname";

    /** The key of the configuration. e.g. false */
    String CRAWLER_DOCUMENT_USE_SITE_ENCODING_ON_ENGLISH = "crawler.document.use.site.encoding.on.english";

(this._months)),e){case"week":return a/7+s/6048e5;case"day":return a+s/864e5;case"hour":return 24*a+s/36e5;case"minute":return 1440*a+s/6e4;case"second":return 86400*a+s/1e3;case"millisecond":return Math.floor(864e5*a)+s;default:throw new Error("Unknown unit "+e)}},Xt.asMilliseconds=jt,Xt.asSeconds=xt,Xt.asMinutes=Pt,Xt.asHours=Ot,Xt.asDays=Wt,Xt.asWeeks=At,Xt.asMonths=Et,Xt.asQuarters=Ft,Xt.asYears=zt,Xt.valueOf=function(){return this.isValid()?this._milliseconds+864e5*this._days+this._months%1...