how to use mysql sandbox to build s - m - m -s topology ？

I want to build this topology

 M1 <-->  M2    
 |        |
 S1       S2

I check sandbox --help, it seems that it only build

M -S

make_replication_sandbox mysql-5.6.tar.gz

M - M

make_replication_sandbox  --master_master mysql-5.6.tar.gz

M - M - M - M (circular)

make_replication_sandbox --circular=4 mysql-5.6.tar.gz

but how can I build

 M1 <-->  M2    
 |        |
 S1       S2