add code comment

Signed-off-by: Kaoutar <[email protected]>

token/core/zkatdlog/crypto/common/array.go

@@ -31,6 +31,7 @@ func (a *G1Array) Bytes() ([]byte, error) {
 		st := hex.EncodeToString(e.Bytes())
 		raw[i] = []byte(st)
 	}
+	// join the serialization of the group elements with the predefined separator.
 	return bytes.Join(raw, []byte(Separator)), nil
 }