This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Optional File Upload { #optional-file-upload }

You can make a file optional by using standard type annotations and setting a default value of `None`:

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

     * does not include the {@linkplain Modular#moduleName() module name} on which it applies.
     *
     * @return the name of the tool option for this path type
     */
    @Nonnull
    @Override
    public Optional<String> option() {
        return Optional.ofNullable(option);
    }

    /**

        return Objects.equals(p, packaging);
    }

    private static Optional<String> getActivationPackaging(org.apache.maven.model.Profile profile) {
        return Optional.ofNullable(profile)
                .map(org.apache.maven.model.Profile::getDelegate)
                .map(Profile::getActivation)
                .map(Activation::getPackaging);

## First dependency "dependable" { #first-dependency-dependable }

You could create a first dependency ("dependable") like:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

It declares an optional query parameter `q` as a `str`, and then it just returns it.

This is quite simple (not very useful), but will help us focus on how the sub-dependencies work.

For example, this model above declares a JSON "`object`" (or Python `dict`) like:

```JSON
{
    "name": "Foo",
    "description": "An optional description",
    "price": 45.2,
    "tax": 3.5
}
```

...as `description` and `tax` are optional (with a default value of `None`), this JSON "`object`" would also be valid:

```JSON

        // As a side effect it will log the optional projects that could not be resolved.
        projectSelector.getOptionalProjectsBySelectors(request, session.getAllProjects(), allOptionalSelectors);
    }

    /**
     * Check whether any of the requested optional profiles were not activated or deactivated.
     * @param session the Maven session.
     * @param profileActivation the requested optional and required profiles.
     */

import org.codelibs.fess.util.BooleanFunction;
import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.QueryResponseList;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.dbflute.util.DfTypeUtil;
import org.lastaflute.taglib.function.LaFunctions;
import org.lastaflute.web.util.LaRequestUtil;
import org.lastaflute.web.util.LaResponseUtil;

   * properties, including:
   *
   * <ul>
   *   <li>{@code java.vendor.version} (added in Java 11, listed as optional as of Java 13)
   *   <li>{@code jdk.module.*} (added in Java 9, optional)
   * </ul>
   */
  public @Nullable String value() {
    return System.getProperty(key);
  }

  /** Returns a string representation of this system property. */

Package: fess
Version: [[version]]
Architecture: all
Maintainer: Fess Team
Depends: libc6, adduser
Section: web
Priority: optional
Homepage: https://github.com/codelibs/fess
Description: Enterprise Search Server: Fess

package org.codelibs.fess.mylasta.direction.sponsor;

import static org.junit.jupiter.api.Assertions.assertNotSame;

import java.util.TimeZone;

import org.codelibs.fess.unit.UnitFessTestCase;
import org.dbflute.optional.OptionalThing;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;
import org.lastaflute.web.ruts.process.ActionRuntime;
import org.lastaflute.web.servlet.request.RequestManager;