code: @CheckResult
      @NonNull
      public final PowerAdapter showOnlyWhile(@NonNull Condition condition) {
          checkNotNull(condition, "condition");
          if (condition instanceof ConstantCondition) {
              if (condition.eval()) {
                  return this;
              } else {
                  return EMPTY;
              }
          }
          return new ConditionalAdapter(this, condition);
      }
docs: Returns a new adapter that presents the items of this adapter only while the specified condition evaluates to
  {@code true}.
  @param condition The condition dictating whether to show the items.
  @return A new adapter.