code: def dsi_dsf_t(si_s, si_t, sf_s, sf_t, sources, targets):
      dsi = si_t - si_s
      dsf = sf_t - sf_s
      velo = dsi / dsf
      sources = sources[(dsi <= 3) & (dsf <= 1)]
      targets = targets[(dsi <= 3) & (dsf <= 1)]
      return dsi, dsf, velo, sources, targets
  
imports: import pytest
  import numpy
  import pandas
  from pandas.testing import assert_frame_equal
  from deepgraph import DeepGraph
label_desc: Use image node_id 8 for calling a global function with example usage: dsi_dsf_t(si_s, si_t, sf_s, sf_t, sources, targets) and returns: dsi,  dsf,  velo,  sources,  targets