Pydantic, que es lo que impulsa toda la validación y serialización de datos en FastAPI, tiene un comportamiento especial cuando usas `Optional` o `Union[Something, None]` sin un valor por defecto, puedes leer más al respecto en la documentación de Pydantic sobre <a href="https://docs.pydantic.dev/2.3/usage/models/#required-optional-fields" class="external-link" target="_blank">Campos requeridos</a>.

///

/// tip | Consejo

import org.dbflute.cbean.ConditionBean;
import org.dbflute.cbean.result.ListResultBean;
import org.dbflute.cbean.result.PagingResultBean;
import org.dbflute.exception.IllegalBehaviorStateException;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.util.DfTypeUtil;
import org.opensearch.action.bulk.BulkRequestBuilder;
import org.opensearch.action.delete.DeleteRequestBuilder;
import org.opensearch.action.index.IndexRequestBuilder;

   * escaped.
   */
  private final boolean[] safeOctets;

  /**
   * Constructs a percent escaper with the specified safe characters and optional handling of the
   * space character.
   *
   * <p>Not that it is allowed, but not necessarily desirable to specify {@code %} as a safe

Das ist keine Limitation von **FastAPI**, sondern Teil des HTTP-Protokolls.

///

## Optionaler Datei-Upload

Sie können eine Datei optional machen, indem Sie Standard-Typannotationen verwenden und den Defaultwert auf `None` setzen:

{* ../../docs_src/request_files/tutorial001_02_an_py310.py hl[9,17] *}

## `UploadFile` mit zusätzlichen Metadaten

import org.codelibs.fess.Constants;
import org.codelibs.fess.dict.DictionaryException;
import org.codelibs.fess.dict.DictionaryFile;
import org.codelibs.fess.util.ComponentUtil;
import org.dbflute.optional.OptionalEntity;

/**
 * Character mapping file handler for managing character mapping dictionaries.
 * This class provides functionality to load, parse, and manage character mapping

import org.codelibs.fess.dict.DictionaryException;
import org.codelibs.fess.dict.DictionaryFile;
import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.KuromojiCSVUtil;
import org.dbflute.optional.OptionalEntity;

/**
 * A dictionary file for Kuromoji.
 */
public class KuromojiFile extends DictionaryFile<KuromojiItem> {
    private static final String KUROMOJI = "kuromoji";

import org.codelibs.core.lang.StringUtil;
import org.codelibs.fess.app.web.base.login.FessCredential;
import org.codelibs.fess.mylasta.action.FessUserBean;
import org.codelibs.fess.util.ComponentUtil;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.login.credential.LoginCredential;
import org.lastaflute.web.util.LaRequestUtil;

import jakarta.annotation.PostConstruct;

/**
 * The helper for user activities.

        SMBUtil.writeInt4(status, hdr, 8);
        // Write Command = SMB2_IOCTL (0x000B) at offset 12
        SMBUtil.writeInt2(0x000B, hdr, 12);
        // Mark as server response to be realistic (optional)
        SMBUtil.writeInt4(0x00000001, hdr, 16); // Flags = SMB2_FLAGS_SERVER_TO_REDIR
        return hdr;
    }

    // Helper: build SMB2 IOCTL response body (without header) with structureSize=49

# Apache Maven Wrapper startup batch script, version 3.3.2
#
# Required ENV vars:
# ------------------
#   JAVA_HOME - location of a JDK home dir
#
# Optional ENV vars
# -----------------
#   MAVEN_OPTS - parameters passed to the Java VM when running Maven
#     e.g. to debug Maven itself, use
#       set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000

cn = "Sally Certowner"

# In how many days, counting from today, this certificate will expire.
expiration_days = 365

# X.509 v3 extensions

# DNS name(s) of the server
dns_name = "localhost"

# (Optional) Server IP address
ip_address = "127.0.0.1"

# Whether this certificate will be used for a TLS server
tls_www_server
```

Run `certtool.exe` and specify the configuration file to generate a certificate: