import static com.google.common.collect.testing.Helpers.copyToSet;
import static java.util.Collections.emptySet;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Collection;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.Nullable;

/**

#6c757d;\n  text-align: left;\n  caption-side: bottom;\n}\n\nth {\n  text-align: inherit;\n  text-align: -webkit-match-parent;\n}\n\nlabel {\n  display: inline-block;\n  margin-bottom: 0.5rem;\n}\n\nbutton {\n  border-radius: 0;\n}\n\nbutton:focus:not(:focus-visible) {\n  outline: 0;\n}\n\ninput,\nbutton,\nselect,\noptgroup,\ntextarea {\n  margin: 0;\n  font-family: inherit;\n  font-size: inherit;\n  line-height: inherit;\n}\n\nbutton,\ninput {\n  overflow: visible;\n}\n\nbutton,\nselect {\n  text-transform:...

 * under the License.
 */
package org.apache.maven.api.plugin.annotations;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.apache.maven.api.annotations.Experimental;

 */

package com.google.common.collect.testing.features;

import static com.google.common.collect.testing.Helpers.copyToSet;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Set}.
 *
 * @author George van den Driessche

 */

package com.google.common.collect.testing.features;

import static com.google.common.collect.testing.Helpers.copyToSet;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.List;
import java.util.Set;

/**
 * Optional features of classes derived from {@code List}.
 *

import com.google.common.collect.Multimap;
import com.google.common.collect.testing.features.Feature;
import com.google.common.collect.testing.features.TesterAnnotation;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Multimap}.
 *
 * @author Louis Wasserman
 */

        default:
          return ImmutableSet.of();
      }
    }

    @Retention(RUNTIME)
    @Inherited
    @TesterAnnotation
    @interface Require {
      ExampleFeature[] value() default {};

      ExampleFeature[] absent() default {};
    }

    @Retention(RUNTIME)
    @Inherited
    @interface NotTesterAnnotation {
      ExampleFeature[] value() default {};

 */

package com.google.common.collect.testing.features;

import static com.google.common.collect.testing.Helpers.copyToSet;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Map;
import java.util.Set;

/**
 * Optional features of classes derived from {@code Map}.
 *

#6c757d;\n  text-align: left;\n  caption-side: bottom;\n}\n\nth {\n  text-align: inherit;\n}\n\nlabel {\n  display: inline-block;\n  margin-bottom: 0.5rem;\n}\n\nbutton {\n  border-radius: 0;\n}\n\nbutton:focus {\n  outline: 1px dotted;\n  outline: 5px auto -webkit-focus-ring-color;\n}\n\ninput,\nbutton,\nselect,\noptgroup,\ntextarea {\n  margin: 0;\n  font-family: inherit;\n  font-size: inherit;\n  line-height: inherit;\n}\n\nbutton,\ninput {\n  overflow: visible;\n}\n\nbutton,\nselect {\n  text-transform:...

We could do better.

We can declare a `UserBase` model that serves as a base for our other models. And then we can make subclasses of that model that inherit its attributes (type declarations, validation, etc).

All the data conversion, validation, documentation, etc. will still work as normally.