class ChangeSet:
    def __init__(self):
        self.operations : list[dict[str, str]] = []

    def add(self, type: str, id: str):
        self.operations.append({ 'operation': 'add', 'type': type, 'id': id })
        return self

    def delete(self, type: str, id: str):
        self.operations.append({ 'operation': 'delete', 'type': type, 'id': id })
        return self

    def update(self, type: str, id: str, properties: list[str]):
        self.operations.append({ 'operation': 'update', 'type': type, 'id': id, 'properties': properties })
        return self

    def append(self, other):
        self.operations += other.operations
        return self

    def compress(self):
        return self