Searching for node in tree recursively

recursive_tree_node_search.py

def _find_node_recursive(self, item, node):
        """Return the node containing the given item in this binary search tree,
        or None if the given item is not found. Search is performed recursively
        starting from the given node (give the root node to start recursion).
        TODO: Best case running time: ??? under what conditions?
        TODO: Worst case running time: ??? under what conditions?"""
        # Check if starting node exists
        if node is None:
            # Not found (base case)
            return None
        # TODO: Check if the given item matches the node's data
        elif ...:
            # Return the found node
            return node
        # TODO: Check if the given item is less than the node's data
        elif ...:
            # TODO: Recursively descend to the node's left child, if it exists
            return ...
        # TODO: Check if the given item is greater than the node's data
        elif ...:
            # TODO: Recursively descend to the node's right child, if it exists
            return ...