code: public final @NotNull S isSameAs(@Nullable A expected) {
      failIfNotSame(customErrorMessage(), rawDescription(), actual, expected);
      return myself();
    }
docs: Verifies that the actual value is the same as the given one.
  
  @param expected the given value to compare the actual value to.
  @return this assertion object.
  @throws AssertionError if the actual value is not the same as the given one.