code: def mean(self):
      return self.base_dist.mean.expand(
          self.batch_shape + self.event_shape
      )
  
imports: import warnings
  from collections import OrderedDict
  from typing import Callable
  import torch
  from torch.distributions.kl import kl_divergence, register_kl
  import pyro.distributions.torch
  from .None import constraints
  from .distribution import Distribution
  from .score_parts import ScoreParts
  from .util import broadcast_shape, scale_and_mask
label_desc: Use image node_id 13 for calling the ExpandedDistribution obj's underlying member method code with example usage: obj.mean() and returns: self