code: def find_particles_in_tile(positions, tile):
      
      bools = tile.contains(positions)
      return np.arange(bools.size)[bools]
docs: Finds the particles in a tile, as numpy.ndarray of ints.
  
      Parameters
      ----------
          positions : `numpy.ndarray`
              [N,3] array of the particle positions to check in the tile
          tile : :class:`peri.util.Tile` instance
              Tile of the region inside which to check for particles.
  
      Returns
      -------
          numpy.ndarray, int
              The indices of the particles in the tile.