code: def _transform_row(self, row):
          
          tmp_row = []
  
          for i, column in enumerate(row.value):
              if column.has_array_value:
                  raise NotImplementedError('array types are not supported')
              elif column.scalar_value.null:
                  tmp_row.append(None)
              else:
                  field_name, rep, mutate_to, cast_from = self._column_data_types[i]
  
                  # get the value from the field_name
                  value = getattr(column.scalar_value, field_name)
  
                  # cast the value
                  if cast_from is not None:
                      value = cast_from(value)
  
                  tmp_row.append(value)
          return tmp_row
docs: Transforms a Row into Python values.
  
          :param row:
              A ``common_pb2.Row`` object.
  
          :returns:
              A list of values casted into the correct Python types.
  
          :raises:
              NotImplementedError