code: def agg(self, v1):
      return v1.sum()
  
imports: from collections import OrderedDict
  import numpy
  import pandas
  import pytest
  from ....None import dataframe
  from ....config import option_context
  from ....core.operand import OperandStage
  from ....tests.core import assert_groupby_equal, require_cudf
  from ....utils import arrow_array_to_objects, pd_release_version
  from ...core import DATAFRAME_OR_SERIES_TYPE
  from ..aggregation import DataFrameGroupByAgg
label_desc: Use image node_id 1 for calling the MockReduction1 obj's underlying member method code with example usage: obj.agg(v1) and returns: v1