def __init__(self, class_id: int | None, leaf_nodes: list[LeafNode]) -> None:
        """
        Create a decision tree representation.

        :param class_id: ID of the class to which this decision tree contributes.
        :param leaf_nodes: A list of leaf nodes of this decision tree.
        """
        self.class_id = class_id
        self.leaf_nodes = leaf_nodes

        Create a decision tree representation.

        :param class_id: ID of the class to which this decision tree contributes.
        :param leaf_nodes: A list of leaf nodes of this decision tree.
        
art/metrics/verification_decisions_trees.py