restrict_actions restricts some actions of an extensive-
form game defined by extensive_form().
restrict_action(game, action)An "extensive_form" class object created by
extensive_form().
A named list of actions that can be chosen by players. The names must be node names: "n1", "n2", etc. A player can choose any action at the nodes that are not listed in this argument.
A "restricted_game" class object in which players have to choose the actions specified by the user.