code: public @NotNull StringAssert doesNotContain(@NotNull String text) {
      checkNotNull(text);
      isNotNull();
      if (!actual.contains(text)) {
        return this;
      }
      failIfCustomMessageIsSet();
      throw failure(format("<%s> should not contain <%s>", actual, text));
    }
docs: Verifies that the actual {@code String} does not contain the given text.
  
  @param text the given text.
  @return this assertion object.
  @throws AssertionError       if the actual {@code String} is {@code null}.
  @throws AssertionError       if the actual {@code String} contains the given text.
  @throws NullPointerException if the given {@code String} is {@code null}.
  @since 1.3