code: def test_regular(self):
      v = pd.Series([101, 102, 103, 104, 105, 106])
      g = pd.Series(["a", "b", "a", "c", "d", "b"])
      answers = ([101, 102], [102, 104], [104], [105])
  
      function = self.primitive().get_function()
      for (_, group), answer in zip(v.groupby(g), answers):
          np.testing.assert_array_equal(function(group), answer)
  
imports: import numpy
  import pandas
  from woodwork.column_schema import ColumnSchema
  from woodwork.logical_types import Datetime
  from featuretools import Feature, GroupByTransformFeature, IdentityFeature, calculate_feature_matrix, feature_base
  from featuretools.computational_backends.feature_set import FeatureSet
  from featuretools.computational_backends.feature_set_calculator import FeatureSetCalculator
  from featuretools.primitives import CumCount, CumMax, CumMean, CumMin, CumSum, Last
  from featuretools.primitives.base import TransformPrimitive
  from featuretools.synthesis import dfs
  from featuretools.tests.testing_utils import feature_with_name
label_desc: Use image node_id 2 for calling the TestCumMean obj's underlying member method code with example usage: obj.test_regular() without return types