docstr: Assign the methods to be called according to the image dimension
  
  Assigns the appropriate functions to be called for displacement field
  inversion, Gaussian pyramid, and affine / dense deformation composition
  according to the dimension of the input images e.g. 2D or 3D.
code: def _connect_functions(self):
      """Assign the methods to be called according to the image dimension
  
      Assigns the appropriate functions to be called for displacement field
      inversion, Gaussian pyramid, and affine / dense deformation composition
      according to the dimension of the input images e.g. 2D or 3D.
      """
      if self.dim == 2:
          self.invert_vector_field = (
              vfu.invert_vector_field_fixed_point_2d
          )
          self.compose = vfu.compose_vector_fields_2d
      else:
          self.invert_vector_field = (
              vfu.invert_vector_field_fixed_point_3d
          )
          self.compose = vfu.compose_vector_fields_3d
  
imports: import logging
  import abc
  import numpy
  import numpy.linalg
  import nibabel
  from nibabel.streamlines import ArraySequence
  from dipy.align import vector_fields
  from dipy.align import floating
  from dipy.align import VerbosityLevels
  from dipy.align import Bunch
  from dipy.align.scalespace import ScaleSpace
label_desc: Use image node_id 4 for calling the SymmetricDiffeomorphicRegistration obj's underlying member method code with example usage: obj._connect_functions() without return types