class_docstr: Implementation of RationalQuadratic kernel:
  
      :math:`k(x, z) = \sigma^2 \left(1 + 0.5 \times \frac{|x-z|^2}{\alpha l^2}
      \right)^{-\alpha}.`
  
  :param torch.Tensor scale_mixture: Scale mixture (:math:`\alpha`) parameter of this
      kernel. Should have size 1.
code: def __init__(
      self,
      input_dim,
      variance=None,
      lengthscale=None,
      scale_mixture=None,
      active_dims=None,
  ):
      super().__init__(input_dim, variance, lengthscale, active_dims)
  
      if scale_mixture is None:
          scale_mixture = torch.tensor(1.0)
      self.scale_mixture = PyroParam(
          scale_mixture, constraints.positive
      )
  
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 RationalQuadratic object from inherited base classes: Isotropy with example: obj = RationalQuadratic(input_dim, variance, lengthscale, scale_mixture, active_dims)