docs: function unique(cells) {
    if(cells.length === 0) {
      return []
    }
    var ptr = 1
      , len = cells.length
    for(var i=1; i<len; ++i) {
      var a = cells[i]
      if(compareCells(a, cells[i-1])) {
        if(i === ptr) {
          ptr++
          continue
        }
        cells[ptr++] = a
      }
    }
    cells.length = ptr
    return cells
  }