code: func (sba *sparseBitArray) Capacity() uint64 {
  	if len(sba.indices) == 0 {
  		return 0
  	}
  
  	return (sba.indices[len(sba.indices)-1] + 1) * s
  }
docs: // Capacity returns the value of the highest possible *seen* value
  // in this sparse bitarray.