code: func New(minShift, depth int) *Index {
  	if minShift == 0 {
  		minShift = DefaultShift
  	}
  	if depth == 0 {
  		depth = DefaultDepth
  	}
  	return &Index{Version: 0x2, minShift: uint32(minShift), depth: uint32(depth)}
  }
docs: // New returns a CSI index with the given minimum shift and depth.
  // The returned index defaults to CSI version 2.