How to use the depccg.tree.Tree.make_binary function in depccg

def rec(node):
            attrib = node.attrib
            if 'terminal' not in attrib:
                cat = Category.parse(attrib['category'])
                children = [rec(spans[child]) for child in attrib['child'].split(' ')]
                if len(children) == 1:
                    return Tree.make_unary(cat, children[0], lang)
                else:
                    assert len(children) == 2
                    left, right = children
                    combinator = guess_combinator_by_triplet(
                                    binary_rules, cat, left.cat, right.cat)
                    combinator = combinator or UNKNOWN_COMBINATOR
                    return Tree.make_binary(cat, left, right, combinator, lang)
            else:
                cat = Category.parse(attrib['category'])
                word = try_get_surface(tokens[attrib['terminal']])
                return Tree.make_terminal(word, cat, lang)

position += 1
        else:
            assert isinstance(stack[-1], Tree)
            children = []
            while isinstance(stack[-1], Tree):
                tree = stack.pop()
                children.append(tree)
            category = stack.pop()
            if len(children) == 1:
                tree = Tree.make_unary(category, children[0], lang)
            elif len(children) == 2:
                right, left = children
                combinator = guess_combinator_by_triplet(
                                binary_rules, category, left.cat, right.cat)
                combinator = combinator or UNKNOWN_COMBINATOR
                tree = Tree.make_binary(category, left, right, combinator, lang)
            else:
                assert False
        stack.append(tree)