code: public @NotNull S isEqualTo(@Nullable A expected) {
      failIfNotEqual(customErrorMessage(), rawDescription(), actual, expected);
      return myself();
    }
docs: Verifies that the actual value is equal to 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 equal to the given one.