By default, what the method `.openapi()` does is check the property `.openapi_schema` to see if it has contents and return them.

If it doesn't, it generates them using the utility function at `fastapi.openapi.utils.get_openapi`.

And that function `get_openapi()` receives as parameters:

* `title`: The OpenAPI title, shown in the docs.
* `version`: The version of your API, e.g. `2.5.0`.

And be compatible with all of them at the same time.

///

Create a utility function to hash a password coming from the user.

And another utility to verify if a received password matches the hash stored.

And another one to authenticate and return a user.

import org.eclipse.aether.artifact.DefaultArtifact;
import org.eclipse.aether.repository.RemoteRepository;
import org.eclipse.aether.repository.RepositoryPolicy;

/**
 * <strong>Warning:</strong> This is an internal utility class that is only public for technical reasons, it is not part
 * of the public API. In particular, this class can be changed or deleted without prior notice.
 *
 * @deprecated since 4.0.0, use {@code maven-api-impl} jar instead

import org.apache.maven.project.ProjectBuildingRequest;
import org.apache.maven.project.ProjectBuildingResult;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utility to select projects for a given set of pom.xml files.
 */
@Named
@Singleton
public class DefaultProjectsSelector implements ProjectsSelector {

These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

///

import static eu.maveniverse.domtrip.maven.MavenPomElements.Elements.PLUGIN;
import static eu.maveniverse.domtrip.maven.MavenPomElements.Elements.VERSION;

/**
 * Utility class for XML operations on Maven POM files.
 *
 * <p>This class provides convenience methods that delegate to:
 * <ul>
 * <li>{@link eu.maveniverse.domtrip.maven.PomEditor} - DomTrip's PomEditor</li>

Because it's a Python exception, you don't `return` it, you `raise` it.

/**
 * Utility class for handling Maven model version operations during upgrades.
 *
 * <p>This class uses domtrip internally for superior formatting preservation
 * and simplified API while maintaining the same external interface.
 */
public final class ModelVersionUtils {

    private ModelVersionUtils() {
        // Utility class
    }

    /**

import static org.mockito.Mockito.doAnswer;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

/**
 * Utility class for creating test fixtures and reducing code duplication in tests.
 */
public final class TestUtils {

    private TestUtils() {
        // Utility class
    }

    /**
     * Creates a mock UpgradeContext with default settings.
     *
     * @return a mock UpgradeContext

//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// Package ioutil implements some I/O utility functions which are not covered
// by the standard library.
package ioutil

import (
	"errors"
	"io"
)

// ErrOverread is returned to the reader when the hard limit of HardLimitReader is exceeded.