Is libvirt internal snapshots are incremental or not..?

Consider the example,

There are 3 snapshots, created respectively snp1 first, 

after some changes snp2, again after some changes snp3.

Question,

1.Is there any dependency that is ...snp2 depended upon snp1 and snp3 depended upon snp2 OR snp1 OR both

2.So if I remove snp2, does it makes snp3 invalid, OR can I use snp3 further.

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