return Collections.unmodifiableSortedSet((SortedSet<E>) collection);
      } else if (collection instanceof Set) {
        return Collections.unmodifiableSet((Set<E>) collection);
      } else if (collection instanceof List) {
        return Collections.unmodifiableList((List<E>) collection);
      } else {
        return Collections.unmodifiableCollection(collection);
      }
    }

        return Collections.unmodifiableSortedSet((SortedSet<E>) collection);
      } else if (collection instanceof Set) {
        return Collections.unmodifiableSet((Set<E>) collection);
      } else if (collection instanceof List) {
        return Collections.unmodifiableList((List<E>) collection);
      } else {
        return Collections.unmodifiableCollection(collection);
      }
    }

          };
        }
      };
    }

    // See Collections.CheckedMap.CheckedEntrySet for details on attacks.

    @Override
    public @Nullable Object[] toArray() {
      synchronized (mutex) {
        /*
         * toArrayImpl returns `@Nullable Object[]` rather than `Object[]` but only because it can
         * be used with collections that may contain null. This collection never contains nulls, so

          };
        }
      };
    }

    // See Collections.CheckedMap.CheckedEntrySet for details on attacks.

    @Override
    public @Nullable Object[] toArray() {
      synchronized (mutex) {
        /*
         * toArrayImpl returns `@Nullable Object[]` rather than `Object[]` but only because it can
         * be used with collections that may contain null. This collection never contains nulls, so

   * @throws IllegalArgumentException if {@code map} is not empty
   * @deprecated Use {@link Collections#newSetFromMap} instead.
   */
  @InlineMe(replacement = "Collections.newSetFromMap(map)", imports = "java.util.Collections")
  @Deprecated
  public static <E extends @Nullable Object> Set<E> newSetFromMap(
      Map<E, Boolean> map) {
    return Collections.newSetFromMap(map);
  }

  /**

   * @throws IllegalArgumentException if {@code map} is not empty
   * @deprecated Use {@link Collections#newSetFromMap} instead.
   */
  @InlineMe(replacement = "Collections.newSetFromMap(map)", imports = "java.util.Collections")
  @Deprecated
  public static <E extends @Nullable Object> Set<E> newSetFromMap(
      Map<E, Boolean> map) {
    return Collections.newSetFromMap(map);
  }

  /**

        final String json = new JsonIndexExportFormatter().format(source, Collections.emptySet());

        assertFalse(json.contains("field_with_null"));
    }

    @Test
    public void test_jsonFormatter_emptyMap() {
        final String json = new JsonIndexExportFormatter().format(Collections.emptyMap(), Collections.emptySet());

        assertTrue(json.contains("{"));

        }

        return new ChatSearchResult(Collections.emptyList(), null, 0L);
    }

    /**
     * Validates a query and returns an empty result if invalid, or null if validation passed.
     */
    private ChatSearchResult validateQuery(final String query) {
        if (StringUtil.isBlank(query)) {
            return new ChatSearchResult(Collections.emptyList(), null, 0L);
        }

        assertEquals("original query", result);
    }

    @Test
    public void test_regenerateQuery_exception_returnsFailedQuery() {
        client.setChatResponse(null); // causes LlmException

        final String result = client.regenerateQuery("test question", "original query", "no_results", Collections.emptyList());

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.truth.Truth.assertWithMessage;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyMap;
import static java.util.Collections.singleton;
import static java.util.Collections.singletonMap;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;