code: def psq2(d1, d2):
      
      d1, d2 = flatten(d1), flatten(d2)
  
      def f(p):
          return sum((p ** 2) * np.nan_to_num(np.log(p * len(p))))
  
      return abs(f(d1) - f(d2))
docs: Compute the PSQ2 measure.
  
      Args:
          d1 (np.ndarray): The first distribution.
          d2 (np.ndarray): The second distribution.