class_docstr: Smoothes TrackVis track files with a B-Spline filter.
  
  Helps remove redundant track points and segments
  (thus reducing the size of the track file) and also
  make tracks nicely smoothed. It will NOT change the
  quality of the tracks or lose any original information.
  
  Example
  -------
  
  >>> import nipype.interfaces.diffusion_toolkit as dtk
  >>> filt = dtk.SplineFilter()
  >>> filt.inputs.track_file = 'tracks.trk'
  >>> filt.inputs.step_length = 0.5
  >>> filt.run()                                 # doctest: +SKIP
code: def _list_outputs(self):
      outputs = self.output_spec().get()
      outputs["smoothed_track_file"] = os.path.abspath(
          self.inputs.output_file
      )
      return outputs
  
file_path: nipype/nipype/interfaces/diffusion_toolkit/postproc.py
imports: import os
  from ..base import TraitedSpec, File, traits, CommandLine, InputMultiPath, CommandLineInputSpec
label_desc: Use image node_id 1 for calling the SplineFilter obj's underlying member method code with example usage: obj._list_outputs() and returns: outputs