First let's see how editors, mypy and other tools would see this.

`BaseUser` has the base fields. Then `UserIn` inherits from `BaseUser` and adds the `password` field, so, it will include all the fields from both models.

We annotate the function return type as `BaseUser`, but we are actually returning a `UserIn` instance.

 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;

  /**
   * Returns the elements of {@code unfiltered} that satisfy a predicate. The returned collection is
   * a live view of {@code unfiltered}; changes to one affect the other.
   *
   * <p>The resulting collection's iterator does not support {@code remove()}, but all other
   * collection methods are supported. When given an element that doesn't satisfy the predicate, the
   * collection's {@code add()} and {@code addAll()} methods throw an {@link

 *       -XepOpt:NullAway:CustomNullableAnnotations=com.google.common.base.ParametricNullness,...,com.google.common.util.concurrent.ParametricNullness},
 *       where the {@code ...} contains the names of all the other {@code ParametricNullness}
 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>

import org.apache.maven.model.building.ModelProblemCollector;
import org.apache.maven.model.building.ModelProblemCollectorRequest;

/**
 * Handles the import of dependency management from other models into the target model.
 *
 * @deprecated use {@link org.apache.maven.api.services.ModelBuilder} instead
 */
@Named
@Singleton
@Deprecated(since = "4.0.0")

 * an expressive source hint for the model problem. Instead, the source hint is configured by the model builder before
 * it delegates to other components that potentially encounter problems. Then, the problem reporter can focus on
 * providing a simple error message, leaving the donkey work of creating a nice model problem to this component.
 *

   * It's unclear whether nulls were to be permitted or forbidden, but presumably the eventual fix
   * will be to permit them, as it seems more likely that code would depend on that behavior than on
   * the other. Thus, we say the bug is in set(), which fails to support null.
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection
  public static Method getSetNullSupportedMethod() {

 *       -XepOpt:NullAway:CustomNullableAnnotations=com.google.common.base.ParametricNullness,...,com.google.common.util.concurrent.ParametricNullness},
 *       where the {@code ...} contains the names of all the other {@code ParametricNullness}
 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>

 *       -XepOpt:NullAway:CustomNullableAnnotations=com.google.common.base.ParametricNullness,...,com.google.common.util.concurrent.ParametricNullness},
 *       where the {@code ...} contains the names of all the other {@code ParametricNullness}
 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>

 *       -XepOpt:NullAway:CustomNullableAnnotations=com.google.common.base.ParametricNullness,...,com.google.common.util.concurrent.ParametricNullness},
 *       where the {@code ...} contains the names of all the other {@code ParametricNullness}
 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>