code: public static MonetaryOperator permil(Number number, MathContext mathContext) {
          return new PermilOperator(new DefaultNumberValue(number).numberValue(BigDecimal.class));
      }
docs: Returns the {@link #percent(BigDecimal)} converting
  this number to {@link BigDecimal} and using the {@link MathContext} in parameters
  @param number to be converted to {@link BigDecimal}
  @param mathContext the mathContext to be used
  @see #permil(BigDecimal)
  @return the permil {@link MonetaryOperator}