docstr: Return the inverse affine transform.
docstr_tok: ["Return","the","inverse","affine","transform","."]
code: def inv(self):
      """
      Return the inverse affine transform.
      """
      a = self.__class__()
      a._precond[:] = self._precond[:]
      a.from_matrix44(spl.inv(self.as_affine()))
      return a
  
imports: import numpy
  import scipy.linalg
  from nibabel.affines import apply_affine
  from transforms3d.quaternions import mat2quat, quat2axangle
  from .transform import Transform
label_desc: Use image node_id 20 for calling the Affine obj's underlying member method code with example usage: obj.inv() and returns: a