code: func (b *OpenBitSet) intersect(other *OpenBitSet) {
  	newLen := b.wlen
  	if other.wlen < newLen {
  		newLen = other.wlen
  	}
  	thisArr := b.bits
  	otherArr := other.bits
  	// testing against zero can be more efficient
  	for pos := newLen - 1; pos >= 0; pos-- {
  		thisArr[pos] &= otherArr[pos]
  	}
  	if b.wlen > newLen {
  		// fill zeros from the new shorter length to the old length
  		for i := newLen; i < b.wlen; i++ {
  			b.bits[i] = 0
  		}
  	}
  	b.wlen = newLen
  }
docs: /* Expert: returns the []int64 storing the bits */
  // func (b *OpenBitSet) RealBits() []int64 { return b.bits }
  // L724