code: def _pdf(self, xloc, dist, length, cache):
          
          output = evaluation.evaluate_density(
              dist, xloc.reshape(1, -1)).reshape(length, -1)
          assert xloc.shape == output.shape
          return output
docs: Probability density function.
  
          Example:
              >>> print(chaospy.Iid(chaospy.Uniform(), 2).pdf(
              ...     [[0.5, 1.5], [0.5, 0.5]]))
              [1. 0.]