code: func (c *Chunk) Encode(span uint32) []byte {
  	return encode(span, FormatGoTszLongWithSpan, c.Series.Bytes())
  }
docs: // Encode encodes the chunk
  // note: chunks don't know their own span, the caller/owner manages that,
  // so for formats that encode it, it needs to be passed in.
  // the returned value contains no references to the chunk. data is copied.