code: def usable_item(self, data):
          
  
          # Use metadata as item
          item = data['meta']
  
          # Add nested IO for data
          elems, elems_is_complex = self.getlist('parameter')
          if elems_is_complex:
              elems = [elem['name'] for elem in elems]
  
          add, add_is_complex = self.getlist('add')
          item['data'] = DataIO(
              data=data['data'],
              parameter=elems,
              add=add,
              start_date=self.getvalue('start_date'),
              end_date=self.getvalue('end_date'),
          )
  
          # TupleMapper will convert item to namedtuple
          return super(StationDataIO, self).usable_item(item)
docs: ACIS web service returns "meta" and "data" for each station; use meta
          attributes as item values, and add an IO for iterating over "data"