import re
import warnings
from collections.abc import Sequence
from copy import copy, deepcopy
from dataclasses import dataclass, is_dataclass
from enum import Enum
from functools import lru_cache
from typing import (
    Annotated,
    Any,
    Union,
    cast,
)

from fastapi._compat import shared
from fastapi.openapi.constants import REF_TEMPLATE
from fastapi.types import IncEx, ModelNameMap, UnionType

        // all, the definition of subscribers on a particular class is totally static
        throw new IllegalArgumentException(
            "missing event subscriber for an annotated method. Is " + listener + " registered?");
      }

      // don't try to remove the set if it's empty; that can't be done safely without a lock

Our codebase uses `null` extensively to represent an absence of value or optionality of the argument.
We utilize nullness annotations in Java code and somewhat rely on IDE warnings to guide us.
However, the Java code we have is not fully annotated, which causes several consequences:
* IDE warnings can be misleading
* Redundant null checks may increase binary size, hurt performance, and increase cognitive load for readers
* Missing null checks may cause NullPointerException

  /**
   * Tests that {@code cls} properly checks null on all constructor and method parameters that
   * aren't annotated nullable (according to the rules of {@link NullPointerTester}). In details:
   *
   * <ul>
   *   <li>All non-private static methods are checked such that passing null for any parameter
   *       that's not annotated nullable should throw {@link NullPointerException}.

import org.jspecify.annotations.Nullable;

/**
 * Tester of subtyping relationships between two types.
 *
 * <p>Tests should inherit from this class, and declare subtyping relationship with public methods
 * annotated by {@link TestSubtype}.
 *
 * <p>These declaration methods rely on Java static type checking to make sure what we want to
 * assert as subtypes are really subtypes according to javac. For example:
 *
 * {@snippet :

import org.jspecify.annotations.Nullable;

/**
 * Tester of subtyping relationships between two types.
 *
 * <p>Tests should inherit from this class, and declare subtyping relationship with public methods
 * annotated by {@link TestSubtype}.
 *
 * <p>These declaration methods rely on Java static type checking to make sure what we want to
 * assert as subtypes are really subtypes according to javac. For example:
 *
 * {@snippet :

 */
public class FeatureEnumTest extends TestCase {
  private static void assertGoodTesterAnnotation(Class<? extends Annotation> annotationClass) {
    assertWithMessage(
            rootLocaleFormat("%s must be annotated with @TesterAnnotation.", annotationClass))
        .that(annotationClass.getAnnotation(TesterAnnotation.class))
        .isNotNull();
    Retention retentionPolicy = annotationClass.getAnnotation(Retention.class);

    return type.getSimpleName() + '@' + i;
  }

  /**
   * Annotates a method to be the instance generator of a certain type. The return type is the
   * generated type. The method parameters correspond to the generated type's type parameters. For
   * example, if the annotated method returns {@code Map<K, V>}, the method signature should be:
   * {@code Map<K, V> generateMap(K key, V value)}.
   */

    return type.getSimpleName() + '@' + i;
  }

  /**
   * Annotates a method to be the instance generator of a certain type. The return type is the
   * generated type. The method parameters correspond to the generated type's type parameters. For
   * example, if the annotated method returns {@code Map<K, V>}, the method signature should be:
   * {@code Map<K, V> generateMap(K key, V value)}.
   */

  }

  public void testNulls() {
    /*
     * Don't bother testing. All non-primitive parameters are used only to construct error messages.
     * We never want to pass null for them, so we haven't annotated them to say that null is
     * allowed. But at the same time, it seems wasteful to bother inserting the checkNotNull calls
     * that NullPointerTester wants.
     *