class_docstr: Abstract class for implementing invertible transformation
  with computable log  det jacobians
  
  Attributes
  ----------
  bijective : bool
class_docstr_tok: ["Abstract","class","for","implementing","invertible","transformation","with","computable","log","det","jacobians","Attributes","--","--","--","--","--","bijective",":","bool"]
code: def inv(self):
      inv = None
      if self._inv is not None:
          inv = self._inv()
      if inv is None:
          inv = _InverseTransformation(self)
          self._inv = weakref.ref(inv)
      return inv
  
imports: import weakref
  from ..distributions.utils import _clip_prob, cached_property, sum_right_most
  from ...block import HybridBlock
  from ....None import np, npx
label_desc: Use image node_id 3 for calling the Transformation obj's underlying member method code with example usage: obj.inv() and returns: inv