code: def is_valid_cpd(self):
      return np.isclose(
          integrate.nquad(
              self.pdf, [[-np.inf, np.inf] for var in self.variables]
          )[0],
          1,
      )
  
imports: import numpy
  from scipy import integrate
  from pgmpy.factors.distributions import BaseDistribution
label_desc: Use image node_id 12 for calling the CustomDistribution obj's underlying member method code with example usage: obj.is_valid_cpd() and returns: np