code: def setUp(self):
      self.m1 = BayesianNetwork([("A", "C"), ("B", "C"), ("D", "B")])
      self.d1 = DataFrame(
          data={
              "A": [0, 0, 1],
              "B": [0, 1, 0],
              "C": [1, 1, 0],
              "D": ["X", "Y", "Z"],
          }
      )
      self.d2 = DataFrame(
          data={
              "A": [0, NaN, 1],
              "B": [0, 1, 0],
              "C": [1, 1, NaN],
              "D": [NaN, "Y", NaN],
          }
      )
  
file_path: pgmpy/pgmpy/tests/test_estimators/test_ParameterEstimator.py
imports: import unittest
  from numpy import NaN
  from pandas import DataFrame
  from pgmpy.estimators import ParameterEstimator
  from pgmpy.models import BayesianNetwork
label_desc: Use image node_id 1 for calling the TestParameterEstimator obj's underlying member method code with example usage: obj.setUp() without return types