code: def transformToNative(obj):
          
          if obj.isNative:
              return obj
          obj.isNative = True
          if obj.value == '':
              obj.value = []
              return obj
          tzinfo = getTzid(getattr(obj, 'tzid_param', None))
          obj.value = [stringToPeriod(x, tzinfo) for x in obj.value.split(",")]
          return obj
docs: Convert comma separated periods into tuples.