class_docstr: This implements the shape augmentation trick of
  Naesseth, Ruiz, Linderman, Blei (2017) https://arxiv.org/abs/1610.05683
code: def expand(self, batch_shape, _instance=None):
      new = self._get_checked_instance(ShapeAugmentedGamma, _instance)
      new = super().expand(batch_shape, new)
      batch_shape = torch.Size(batch_shape)
      new.concentration = self.concentration.expand(batch_shape)
      new._boost = self._boost
      new._rejection_gamma = self._rejection_gamma.expand(batch_shape)
      new._validate_args = self._validate_args
      return new
  
imports: import torch
  from pyro.distributions.rejector import Rejector
  from pyro.distributions.score_parts import ScoreParts
  from pyro.distributions.torch import Beta, Dirichlet, Gamma, Normal
  from pyro.distributions.util import copy_docs_from, weakmethod
label_desc: Use image node_id 2 for calling the ShapeAugmentedGamma obj's underlying member method code with example usage: obj.expand(batch_shape, _instance) and returns: new