class_docstr: Implementation of Matern52 kernel:
  
      :math:`k(x,z)=\sigma^2\left(1+\sqrt{5}\times\frac{|x-z|}{l}+\frac{5}{3}\times
      \frac{|x-z|^2}{l^2}\right)\exp\left(-\sqrt{5} \times \frac{|x-z|}{l}\right).`
code: def __init__(
      self, input_dim, variance=None, lengthscale=None, active_dims=None
  ):
      super().__init__(input_dim, variance, lengthscale, active_dims)
  
imports: import torch
  from torch.distributions import constraints
  from pyro.contrib.gp.kernels.kernel import Kernel
  from pyro.nn.module import PyroParam
label_desc: Use image node_id 1 to create a new Matern52 object from inherited base classes: Isotropy with example: obj = Matern52(input_dim, variance, lengthscale, active_dims)