docs: public final void contains(@NullableDecl Object element) {
      if (!Iterables.contains(actual(), element)) {
        List<Object> elementList = newArrayList(element);
        if (hasMatchingToStringPair(actual(), elementList)) {
          failWithoutActual(
              fact("expected to contain", element),
              fact("an instance of", objectToTypeName(element)),
              simpleFact("but did not"),
              fact(
                  "though it did contain",
                  countDuplicatesAndAddTypeInfo(
                      retainMatchingToString(actual(), elementList /* itemsToCheck */))),
              fullContents());
        } else {
          failWithActual("expected to contain", element);
        }
      }
    }