code: public @NotNull StringAssert isEqualToIgnoringCase(String expected) {
      if (actual == null && expected == null) {
        return this;
      }
      isNotNull();
      if (actual.equalsIgnoreCase(expected)) {
        return this;
      }
      failIfCustomMessageIsSet();
      throw failure(format("<%s> should be equal to :<%s> ignoring case", actual, expected));
    }
docs: Verifies that the actual {@code String} is equal to the given one ignoring case.
  
  @param expected the given {@code String} to compare the actual {@code String} to.
  @return this assertion object.
  @throws AssertionError if the actual {@code String} is {@code null}.
  @throws AssertionError if the actual {@code String} is not equal to the given one ignoring case.