class ShouldContainOnlyNulls extends BasicErrorMessageFactory {

  /**
   * Creates a new <code>{@link ShouldContainOnlyNulls}</code>.
   * @param actual the actual value in the failed assertion.
   * @return the created {@code ErrorMessageFactory}.
   */
  public static ErrorMessageFactory shouldContainOnlyNulls(Object actual) {
    return new ShouldContainOnlyNulls(actual, EMPTY, null);
  }

  public static ErrorMessageFactory shouldContainOnlyNulls(Object actual, Iterable<?> nonNullElements) {
    return new ShouldContainOnlyNulls(actual, NON_NULL_ELEMENTS, nonNullElements);
  }

  private ShouldContainOnlyNulls(Object actual, ErrorType errorType, Iterable<?> notExpected) {
    super("%n" +
          "Expecting actual:%n" +
          "  %s%n" +
          "to contain only null elements but " + describe(errorType),
          actual, notExpected);
  }

  private static String describe(ErrorType errorType) {<FILL_FUNCTION_BODY>}

  public enum ErrorType {
    EMPTY, NON_NULL_ELEMENTS
  }
}

    switch (errorType) {
    case EMPTY:
      return "it was empty";
    case NON_NULL_ELEMENTS:
    default:
      return "some elements were not:%n  %s";
    }
  
<methods>public transient void <init>(java.lang.String, java.lang.Object[]) ,public java.lang.String create(org.assertj.core.description.Description, org.assertj.core.presentation.Representation) ,public java.lang.String create(org.assertj.core.description.Description) ,public java.lang.String create() ,public boolean equals(java.lang.Object) ,public int hashCode() ,public java.lang.String toString() <variables>protected final non-sealed java.lang.Object[] arguments,protected final non-sealed java.lang.String format,org.assertj.core.error.MessageFormatter formatter