docstr: Creates a zero displacement field
  
  Creates a zero displacement field (the identity transformation).
code: def allocate(self):
      """Creates a zero displacement field
  
      Creates a zero displacement field (the identity transformation).
      """
      self.forward = np.zeros(
          tuple(self.disp_shape) + (self.dim,), dtype=floating
      )
      self.backward = np.zeros(
          tuple(self.disp_shape) + (self.dim,), dtype=floating
      )
  
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 5 for calling the DiffeomorphicMap obj's underlying member method code with example usage: obj.allocate() without return types