code: public Effort effort(double value, Workitem item, Member member,
                           DateTime date) throws IllegalStateException {
          return effort(value, item, member, date, null);
      }
docs: Create a new effort record with a value and date, assigned to the given
  workitem and member.
  
  @param value  the value of the effort record.
  @param item   the workitem to assign the effort record to.
  @param member the member to assign the effort record to. If is null then
  member not set.
  @param date   the date to log the effort record against. If is null then
  date not set.
  @return A newly minted Effort Record that exists in the VersionOne
  system.
  @throws IllegalStateException if Effort tracking is not enabled.