def bst_contains(node, value):
    """
    Return whether tree rooted at node contains value.

    Assume node is the root of a Binary Search Tree

    @param BinaryTree|None node: node of a Binary Search Tree
    @param object value: value to search for
    @rtype: bool

    >>> bst_contains(None, 5)
    False
    >>> bst_contains(BinaryTree(7, BinaryTree(5), BinaryTree(9)), 5)
    True
    """
    if node is None:
        return False
    elif node.data == value:
        return True
    elif value < node.data:
        return bst_contains(node.left, value)
    elif value > node.data:
        return bst_contains(node.right, value)
    else:
        assert False, "WTF!"