d, err := config.getDriver(ctx, tier)
	if err != nil {
		return err
	}
	return checkWarmBackend(ctx, d)
}

// Empty returns if tier targets are empty
func (config *TierConfigMgr) Empty() bool {
	if config == nil {
		return true
	}
	return len(config.ListTiers()) == 0
}

// TierType returns the type of tier

  @SuppressWarnings("unchecked") // empty Object[] as E[]
  public static <E extends @Nullable Object> MinimalSet<E> of(E... contents) {
    return ofClassAndContents(Object.class, (E[]) new Object[0], asList(contents));
  }

  @SuppressWarnings("unchecked") // empty Object[] as E[]
  public static <E extends @Nullable Object> MinimalSet<E> from(Collection<? extends E> contents) {

		t.Fatalf("joins NamedPet and Account should not empty:%v", user1)
	}

	// Account should empty
	DB.Delete(&user1.Account)

	var user2 User
	DB.Model(&User{}).Joins("NamedPet").Joins("Account").First(&user2, user.ID)
	if user2.NamedPet == nil || user2.Account.ID != 0 {
		t.Fatalf("joins Account should not empty:%v", user2)
	}

	// NamedPet should empty
	DB.Delete(&user1.NamedPet)

	var user3 User

   *
   * <p>If you only want to calculate the mean, use {@link #meanOf} instead of creating a {@link
   * Stats} instance.
   *
   * @throws IllegalStateException if the dataset is empty
   */
  public double mean() {
    checkState(count != 0);
    return mean;
  }

  /**
   * Returns the sum of the values.
   *
   * <h3>Non-finite values</h3>
   *

 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public class MoreCollectorsTest extends TestCase {
  public void testToOptionalEmpty() {
    assertThat(Stream.empty().collect(toOptional())).isEmpty();
  }

  public void testToOptionalSingleton() {
    assertThat(Stream.of(1).collect(toOptional())).hasValue(1);
  }

  public void testToOptionalNull() {

     *
     * @param content The String representation, may be empty or {@code null}.
     */
    public StringSource(CharSequence content) {
        this(content, null);
    }

    /**
     * Creates a new source backed by the specified string.
     *
     * @param content The String representation, may be empty or {@code null}.
     * @param location The location to report for this use, may be {@code null}.

		predCount++
	}
	if f.ObjectSizeLessThan != 0 {
		pType = sizeLtPred
		predCount++
	}
	// Note: S3 supports empty <Filter></Filter>, so predCount == 0 is
	// valid.
	if predCount > 1 {
		return errInvalidFilter
	}

	var err error
	switch pType {
	case nonePred:
	// S3 supports empty <Filter></Filter>
	case prefixPred:
	case andPred:
		err = f.And.Validate()
	case tagPred:

   * permutation, instead of two. This is why the elements have to implement {@link Comparable}.
   *
   * <p>An empty iterable has only one permutation, which is an empty list.
   *
   * <p>This method is equivalent to {@code Collections2.orderedPermutations(list,
   * Ordering.natural())}.
   *

@Immutable
@ElementTypesAreNonnullByDefault
public final class ImmutableDoubleArray implements Serializable {
  private static final ImmutableDoubleArray EMPTY = new ImmutableDoubleArray(new double[0]);

  /** Returns the empty array. */
  public static ImmutableDoubleArray of() {
    return EMPTY;
  }

  /** Returns an immutable array containing a single value. */
  public static ImmutableDoubleArray of(double e0) {

				"x-amz-meta-key": []string{"amz-meta1", "amz-meta2"},
			},
			metadata: map[string]string{
				"x-amz-meta-key": "amz-meta1,amz-meta2",
			},
			shouldFail: false,
		},
		// Empty header input returns empty metadata.
		{
			header:     nil,
			metadata:   nil,
			shouldFail: true,
		},
	}

	// Validate if the extracting headers.
	for i, testCase := range testCases {