docs: def build(self, builder):
          """Build XML by appending to builder"""
  
          params = dict(
              OID=self.oid,
              Name=self.name,
              Repeating=bool_to_yes_no(self.repeating),
              Type=self.event_type,
          )
  
          if self.category is not None:
              params["Category"] = self.category
  
          if self.access_days is not None:
              params["mdsol:AccessDays"] = str(self.access_days)
  
          if self.start_win_days is not None:
              params["mdsol:StartWinDays"] = str(self.start_win_days)
  
          if self.target_days is not None:
              params["mdsol:TargetDays"] = str(self.target_days)
  
          if self.end_win_days is not None:
              params["mdsol:EndWinDays"] = str(self.end_win_days)
  
          if self.overdue_days is not None:
              params["mdsol:OverDueDays"] = str(self.overdue_days)
  
          if self.close_days is not None:
              params["mdsol:CloseDays"] = str(self.close_days)
  
          builder.start("StudyEventDef", params)
          for formref in self.formrefs:
              formref.build(builder)
          for alias in self.aliases:
              alias.build(builder)
          builder.end("StudyEventDef")