code: public static BigInteger checkIncludedInBig(
      final BigInteger x,
      final String x_name,
      final RangeInclusiveB range,
      final String range_name)
    {
      Objects.requireNonNull(x, "Value");
      Objects.requireNonNull(x_name, "Value name");
      Objects.requireNonNull(range, "Range");
      Objects.requireNonNull(range_name, "Range name");
  
      if (range.includesValue(x)) {
        return x;
      }
  
      final var message = String.format(
        "%s <= %s (%s) <= %s (%s) == false",
        range.lower(),
        x_name,
        x,
        range.upper(),
        range_name);
  
      throw new RangeCheckException(message);
    }
docs: <p> Assert that {@code x} (named {@code x_name}) is included in the given
  range {@code range} (named {@code range_name}). </p>
  
  @param x          The checked value
  @param x_name     The name of the checked value
  @param range      The inclusive range
  @param range_name The name of the inclusive range
  
  @return x