[Serialization and deserialization] How to save a flowchart ?

[gemmi]

I have tried this flowchart and attracted by it, it's architecture is natural and lucid, now i want to ask a question further, that is how to serialize a flowchart object to save it and then deserialize it for next modification?
In flowchart libs like JointJS there are functions of graph/canvas called "toJSON" and "fromJSON" to implement serialization and deserialization(serialize all elements, include canvas, all links, all boxes, and so on), which are easy to use. I think we should also take this into account.