code: private Duration getRangeDurationSubDay(ProjectCalendar projectCalendar, TimescaleUnits rangeUnits, DateRange range, List<TimephasedWork> assignments, int startIndex)
     {
        throw new UnsupportedOperationException("Please request this functionality from the MPXJ maintainer");
     }
docs: For a given date range, determine the duration of work, based on the
  timephased resource assignment data.
  
  This method deals with timescale units of less than a day.
  
  @param projectCalendar calendar used for the resource assignment calendar
  @param rangeUnits timescale units
  @param range target date range
  @param assignments timephased resource assignments
  @param startIndex index at which to start searching through the timephased resource assignments
  @return work duration