Assertion: python's scale | /r/MadeOf | keratin
Facets:
Source sentences:
text: The scales of all snakes (and many lizard species) are made of keratin, which is the same substance that makes up the hair and fingernails of humans.
text: They are largely covered in scales made of keratin—the same material as human fingernails—which gives them the nickname "scaly anteater.