code: public String getAsString(SizeUnit...sizeUnits)
    {
      if(sizeUnits == null || sizeUnits.length == 0)
        return toString();
      
      return getAsString(CollectionsUtils.toEnumSet(SizeUnit.class, sizeUnits));
    }
docs: Return a string representation of this instance using the given units
  E.g. 2g3m4k given units g/m -> "2g3m"
  2g3m4k given units g/k -> "2g3076k"
  3m4k given units t/g -> "0g"
  2g3m given units k/b -> "2100224k"
  
  @param sizeUnits the sizeUnits you want in the decomposition
  @return a string representation of this instance using the given units.