code: def pore_to_pore(target):
      r
      network = target.project.network
      throats = network.throats(target.name)
      conns = network['throat.conns']
      P1 = conns[:, 0]
      P2 = conns[:, 1]
      coords = network['pore.coords']
      vec = coords[P2] - coords[P1]
      unit_vec = tr.unit_vector(vec, axis=1)
      return unit_vec[throats]
docs: r"""
      Calculates throat vector as straight path between connected pores.
  
      Parameters
      ----------
      geometry : OpenPNM Geometry object
          The object containing the geometrical properties of the throats
  
      Notes
      -----
      There is an important impicit assumption here: the positive direction is
      taken as the direction from the pore with the lower index to the higher.
      This corresponds to the pores in the 1st and 2nd columns of the
      'throat.conns' array as stored on the etwork.