code: def test_aggregate_sum_invalid(self):
      tableset = TableSet(self.tables.values(), self.tables.keys())
  
      with self.assertRaises(DataTypeError):
          tableset.aggregate([("letter_sum", Sum("letter"))])
  
imports: from collections import OrderedDict
  from decimal import Decimal
  from agate import Table, TableSet
  from agate.aggregations import Count, MaxLength, Mean, Min, Sum
  from agate.data_types import Number, Text
  from agate.exceptions import DataTypeError
  from agate.testcase import AgateTestCase
label_desc: Use image node_id 9 for calling the TestAggregate obj's underlying member method code with example usage: obj.test_aggregate_sum_invalid() without return types