code: def forward(ctx, nat_mean, nat_covar):
      mu, L = _NaturalToMuVarSqrt._forward(nat_mean, nat_covar)
      ctx.save_for_backward(mu, L)
      return mu, L
  
imports: import abc
  import torch
  from linear_operator.operators import CholLinearOperator, TriangularLinearOperator
  from linear_operator.utils.cholesky import psd_safe_cholesky
  from ..distributions import MultivariateNormal
  from ._variational_distribution import _VariationalDistribution
label_desc: Use image node_id 2 for calling the _NaturalToMuVarSqrt obj's underlying member method code with example usage: obj.forward(ctx, nat_mean, nat_covar) and returns: mu,  L