}

          @Override
          public String toString() {
            return "theDelegate";
          }
        };
    Executor sequential1 = newSequentialExecutor(delegate);
    Executor sequential2 = newSequentialExecutor(delegate);
    assertThat(sequential1.toString()).contains("theDelegate");
    assertThat(sequential1.toString()).isNotEqualTo(sequential2.toString());

 * </ul>
 *
 * <p>This class is similar to {@link MoreExecutors#newSequentialExecutor}. This class is different
 * in a few ways:
 *
 * <ul>
 *   <li>Each task may be associated with a different executor.
 *   <li>Tasks may be of type {@code AsyncCallable}.
 *   <li>Running tasks <i>cannot</i> be interrupted. (Note that {@code newSequentialExecutor} does