Assertion: python | /r/CapableOf | stiffen their ribs
Facets:
value: for support against the ground
type: PURPOSE
Source sentences:
text: Pythons stiffen their ribs for support against the ground then lift their bellies and push themselves forward.
text: To achieve this “rectilinear progression” movement, they stiffen their ribs for support against the ground, lift their bellies, and push themselves forward.