code: def forward(ctx, input, ewma):
      ctx.save_for_backward(ewma)
      return input.log()
  
imports: import math
  import warnings
  import torch
  import pyro
  from pyro import poutine
  from pyro.contrib.oed.search import Search
  from pyro.contrib.util import lexpand
  from pyro.infer import SVI, EmpiricalMarginal, Importance
  from pyro.infer.autoguide.utils import mean_field_entropy
  from pyro.util import torch_isinf, torch_isnan
label_desc: Use image node_id 1 for calling the _EwmaLogFn obj's underlying member method code with example usage: obj.forward(ctx, input, ewma) and returns: input