code: public @NotNull StringAssert doesNotMatch(String regex) {
      isNotNull();
      if (!actual.matches(regex)) {
        return this;
      }
      failIfCustomMessageIsSet();
      throw failure(format("<%s> should not match the regular expression:<%s>", actual, regex));
    }
docs: Verifies that the actual {@code String} does not match the given one.
  
  @param regex the given regular expression expected not to be matched by the actual one.
  @return this assertion object.
  @throws AssertionError if the actual {@code String} is {@code null}.
  @throws AssertionError if the actual {@code String} matches the given regular expression.