Type Alias SelectionFunction 

pub type SelectionFunction<const N: usize> = fn(value: f64, policy: f64, n_visits: f64, parent_n_visits: f64, exploration_coef: f64) -> f64;

Type alias for a function pointer used to determine a node’s selection score during MCTS.

This function takes the following parameters:

• value: The current mean value of the node.
• policy: The initial policy probability for the action leading to this node (from the parent’s perspective).
• n_visits: The number of times the node has been visited.
• parent_n_visits: The number of times the parent node has been visited.
• exploration_coef: The exploration coefficient from MctsConfig.

It returns an f64 score used to rank nodes for selection.