class_docstr: Implementation of Cosine kernel:
  
      :math:`k(x,z) = \sigma^2 \cos\left(\frac{|x-z|}{l}\right).`
  
  :param torch.Tensor lengthscale: Length-scale parameter of this kernel.
code: def __init__(
      self, input_dim, variance=None, lengthscale=None, active_dims=None
  ):
      super().__init__(input_dim, variance, lengthscale, active_dims)
  
file_path: pyro/pyro/contrib/gp/kernels/periodic.py
imports: import math
  import torch
  from torch.distributions import constraints
  from pyro.contrib.gp.kernels.isotropic import Isotropy
  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 Cosine object from inherited base classes: Isotropy with example: obj = Cosine(input_dim, variance, lengthscale, active_dims)