import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.codelibs.core.io.CloseableUtil;

```Python
from datetime import date

from pydantic import BaseModel

# Déclarez une variable comme étant une str
# et profitez de l'aide de l'éditeur dans cette fonction
def main(user_id: str):
    return user_id


# Un modèle Pydantic
class User(BaseModel):
    id: int
    name: str
    joined: date
```

Qui peuvent ensuite être utilisés comme ceci :

```Python

                return LocalDateTime.ofInstant(instant, ZoneId.systemDefault());
            } catch (final DateTimeParseException e) {
                logger.debug("Invalid date format: {}", value, e);
            }
        }
        return DfTypeUtil.toLocalDateTime(value);
    }

            <input type="text" id="messageText" autocomplete="off"/>
            <button>Send</button>
        </form>
        <ul id='messages'>
        </ul>
        <script>
            var client_id = Date.now()
            document.querySelector("#ws-id").textContent = client_id;
            var ws = new WebSocket(`ws://localhost:8000/ws/${client_id}`);
            ws.onmessage = function(event) {

Declara los **parámetros de header** que necesitas en un **modelo Pydantic**, y luego declara el parámetro como `Header`:

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

**FastAPI** **extraerá** los datos para **cada campo** de los **headers** en el request y te dará el modelo Pydantic que definiste.

## Revisa la Documentación { #check-the-docs }

Puedes ver los headers requeridos en la interfaz de documentación en `/docs`:

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.Date;

import org.codelibs.fess.dict.DictionaryException;
import org.codelibs.fess.dict.DictionaryFile.PagingList;
import org.codelibs.fess.helper.SystemHelper;
import org.codelibs.fess.unit.UnitFessTestCase;

                }
            }
        }
    }

    /**
     * Parses a date/time string and converts it to UTC timezone.
     *
     * @param value The date/time string to parse
     * @param formatter The date/time formatter to use
     * @return LocalDateTime in UTC timezone
     */

from pydantic_core import PydanticUndefinedType

from ._compat import (
    Url,
    is_pydantic_v1_model_instance,
)


# Taken from Pydantic v1 as is
def isoformat(o: datetime.date | datetime.time) -> str:
    return o.isoformat()


# Adapted from Pydantic v1
# TODO: pv2 should this return strings instead?
def decimal_encoder(dec_value: Decimal) -> int | float:
    """

     */
    @Deprecated
    String getBaseDirectory();

    // Timing (remove this)
    @Deprecated
    MavenExecutionRequest setStartTime(Date start);

    @Deprecated
    Date getStartTime();

    MavenExecutionRequest setStartInstant(Instant start);

    Instant getStartInstant();

    // Goals
    MavenExecutionRequest setGoals(List<String> goals);

    public void format(MessageBuilder builder, long size, ScaleUnit unit) {
        format(builder, size, unit, false);
    }

    public void formatRate(MessageBuilder builder, double rate) {
        // Handle invalid rates gracefully (including negative values)
        if (Double.isNaN(rate) || Double.isInfinite(rate) || rate < 0) {
            builder.append("? B/s");
            return;
        }