code: func (c *Codec) Encode(chk *Chunk) []byte {
  	buffer := make([]byte, 0, chk.MemoryUsage())
  	for _, col := range chk.columns {
  		buffer = c.encodeColumn(buffer, col)
  	}
  	return buffer
  }
docs: // Encode encodes a Chunk to a byte slice.