Private knowledge

What each player learned in secret is kept in GameState.knowledge, so it survives after transient fields such as drawn_policies are cleared. Each entry is a frozen subclass of Knowledge with the uid of the player who learned it:

Knowledge	Recorded when
PresidentDrawKnowledge	A president draws 3 policies after a passed election
ChancellorReceiveKnowledge	A chancellor receives 2 policies from the president
PeekKnowledge	A president peeks at the top 3 policies
InvestigationKnowledge	A president learns the party of an investigated player

scrub_state keeps only the viewer's own entries, so an agent never sees what another player learned.

What else scrub_state hides

scrub_state(state, viewer_uid) returns a new state for one viewer. Besides other players' knowledge, it hides:

• other players' parties and roles, unless the viewer's role reveals them; an investigation reveals only the party,
• the contents of the draw and discard piles, though not their sizes,
• the policies in hand, unless the viewer is holding them,
• other players' votes while an election is still open,
• an investigation result the viewer didn't find,
• the state of the random generator that shuffles the deck.

Hidden values are replaced with the HIDDEN sentinel. Fascists see every fascist and Hitler. Hitler sees the fascists only in 5- and 6-player games. Liberals see nobody.