code: def add_boundary_pores(self, labels=['top', 'bottom', 'front', 'back',
                                           'left', 'right'], offset=None):
          r
          offset = sp.array(offset)
          if offset.size == 1:
              offset = sp.ones(3)*offset
          for item in labels:
              Ps = self.pores(item)
              coords = sp.absolute(self['pore.coords'][Ps])
              axis = sp.count_nonzero(sp.diff(coords, axis=0), axis=0) == 0
              ax_off = sp.array(axis, dtype=int)*offset
              if sp.amin(coords) == sp.amin(coords[:, sp.where(axis)[0]]):
                  ax_off = -1*ax_off
              topotools.add_boundary_pores(network=self, pores=Ps, offset=ax_off,
                                           apply_label=item + '_boundary')
docs: r"""
          Add boundary pores to the specified faces of the network
  
          Pores are offset from the faces of the domain.
  
          Parameters
          ----------
          labels : string or list of strings
              The labels indicating the pores defining each face where boundary
              pores are to be added (e.g. 'left' or ['left', 'right'])
  
          offset : scalar or array_like
              The spacing of the network (e.g. [1, 1, 1]).  This must be given
              since it can be quite difficult to infer from the network,
              for instance if boundary pores have already added to other faces.