code: def test_regular_alpha_var():
      primitive_instance = ExponentialWeightedVariance(alpha=0.8)
      primitive_func = primitive_instance.get_function()
      array = pd.Series([1, 2, 7, 5])
      answer = pd.Series(primitive_func(array))
      correct_answer = pd.Series(
          [np.nan, 0.5, 12.999999999999996, 2.996898263027294]
      )
      pd.testing.assert_series_equal(answer, correct_answer)
  
imports: import numpy
  import pandas
  from featuretools.primitives import ExponentialWeightedAverage, ExponentialWeightedSTD, ExponentialWeightedVariance
label_desc: Use image node_id 16 for calling a global function with example usage: test_regular_alpha_var() without return types