code: def map_index_val(index_val):
          
          if index_val is None:
              return DynamoMappings.NONE_VAL
  
          index_val = str(index_val)
          if not index_val:
              return DynamoMappings.EMPTY_STR_VAL
  
          return index_val
docs: Xform index_val so that it can be stored/queried.