<｜begin▁of▁sentence｜>### Instruction:
Imagine you're constructing a developmental milestones chart to keep track of various growth stages in children. Each number represents a specific stage, and the directed connections denote the typical progression from one stage to another. Now, in this scenario, we're working with a sequence of progressions: from stage 1 to stage 2, stage 1 to stage 3, stage 2 to stage 4, and stage 3 to stage 4. 

Consider an antichain as a set of developmental stages that are independent; that is, none of the stages directly follows another. It's like when children are learning to speak, write, and walk—each task is tackled in its own time without one being a prerequisite for another. Could you please shed light on all the distinct combinations of such independent stages, or "antichains", within this model of development? This would help us better understand the variety of developmental paths a child could take without one milestone necessarily leading to the next.
### Response:
import networkx as nx

# Create a directed acyclic graph (DAG)
DG = nx.DiGraph([(1, 2), (1, 3), (2, 4), (3, 4)])

# Generate antichains from the DAG
antichains_list = list(nx.antichains(DG))

print(antichains_list)
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