code: def default_ta(tr, nslices):
      slice_time = tr / float(nslices)
      return slice_time * (nslices - 1)
  
imports: import gzip
  import sys
  from copy import deepcopy
  from glob import glob
  from os.path import abspath, isfile, splitext
  from os.path import join
  from warnings import warn
  import numpy
  import nipy.interfaces.matlab
  from nipy.interfaces.spm import fltcols, fname_presuffix, fnames_presuffix, make_job, run_jobdef, scans_for_fnames, spm_info
label_desc: Use image node_id 3 for calling a global function with example usage: default_ta(tr, nslices) and returns: unknown