code: func (bitmap *bitmap) String() string {
  	div, mod := bitmap.Size>>3, bitmap.Size&0x07
  	buff := make([]string, div+mod)
  
  	for i := 0; i < div; i++ {
  		buff[i] = fmt.Sprintf("%08b", bitmap.data[i])
  	}
  
  	for i := div; i < div+mod; i++ {
  		buff[i] = fmt.Sprintf("%1b", bitmap.Bit(div*8+(i-div)))
  	}
  
  	return strings.Join(buff, "")
  }
docs: // String returns the bit sequence string of the bitmap.