How to use the mutmut.cache.Line function in mutmut

def update_line_numbers(filename):
    hash = hash_of(filename)
    sourcefile = get_or_create(SourceFile, filename=filename)
    if hash == sourcefile.hash:
        return
    cached_line_objects = list(sourcefile.lines.order_by(Line.line_number))

    cached_lines = [x.line for x in cached_line_objects]

    with open(filename) as f:
        existing_lines = [x.strip('\n') for x in f.readlines()]

    if not cached_lines:
        for i, line in enumerate(existing_lines):
            Line(sourcefile=sourcefile, line=line, line_number=i)
        return

    for command, a, a_index, b, b_index in sequence_ops(cached_lines, existing_lines):
        if command == 'equal':
            if a_index != b_index:
                cached_obj = cached_line_objects[a_index]
                assert cached_obj.line == existing_lines[b_index]

def update_line_numbers(filename):
    hash = hash_of(filename)
    sourcefile = get_or_create(SourceFile, filename=filename)
    if hash == sourcefile.hash:
        return
    cached_line_objects = list(sourcefile.lines.order_by(Line.line_number))

    cached_lines = [x.line for x in cached_line_objects]

    with open(filename) as f:
        existing_lines = [x.strip('\n') for x in f.readlines()]

    if not cached_lines:
        for i, line in enumerate(existing_lines):
            Line(sourcefile=sourcefile, line=line, line_number=i)
        return

    for command, a, a_index, b, b_index in sequence_ops(cached_lines, existing_lines):
        if command == 'equal':
            if a_index != b_index:
                cached_obj = cached_line_objects[a_index]
                assert cached_obj.line == existing_lines[b_index]
                cached_obj.line_number = b_index

        elif command == 'delete':
            cached_line_objects[a_index].delete()

        elif command == 'insert':
            if b is not None:
                Line(sourcefile=sourcefile, line=b, line_number=b_index)

class SourceFile(db.Entity):
    filename = Required(str, autostrip=False)
    hash = Optional(str)
    lines = Set('Line')


class Line(db.Entity):
    sourcefile = Required(SourceFile)
    line = Optional(str, autostrip=False)
    line_number = Required(int)
    mutants = Set('Mutant')


class Mutant(db.Entity):
    line = Required(Line)
    index = Required(int)
    tested_against_hash = Optional(str, autostrip=False)
    status = Required(str, autostrip=False)  # really an enum of mutant_statuses


def init_db(f):
    @wraps(f)
    def wrapper(*args, **kwargs):
        if db.provider is None:
            cache_filename = os.path.join(os.getcwd(), '.mutmut-cache')
            db.bind(provider='sqlite', filename=cache_filename, create_db=True)

            try:
                db.generate_mapping(create_tables=True)
            except OperationalError:
                pass

cached_obj = cached_line_objects[a_index]
                assert cached_obj.line == existing_lines[b_index]
                cached_obj.line_number = b_index

        elif command == 'delete':
            cached_line_objects[a_index].delete()

        elif command == 'insert':
            if b is not None:
                Line(sourcefile=sourcefile, line=b, line_number=b_index)

        elif command == 'replace':
            if a_index is not None:
                cached_line_objects[a_index].delete()
            if b is not None:
                Line(sourcefile=sourcefile, line=b, line_number=b_index)

        else:
            raise ValueError('Unknown opcode from SequenceMatcher: {}'.format(command))

    sourcefile.hash = hash

Line(sourcefile=sourcefile, line=line, line_number=i)
        return

    for command, a, a_index, b, b_index in sequence_ops(cached_lines, existing_lines):
        if command == 'equal':
            if a_index != b_index:
                cached_obj = cached_line_objects[a_index]
                assert cached_obj.line == existing_lines[b_index]
                cached_obj.line_number = b_index

        elif command == 'delete':
            cached_line_objects[a_index].delete()

        elif command == 'insert':
            if b is not None:
                Line(sourcefile=sourcefile, line=b, line_number=b_index)

        elif command == 'replace':
            if a_index is not None:
                cached_line_objects[a_index].delete()
            if b is not None:
                Line(sourcefile=sourcefile, line=b, line_number=b_index)

        else:
            raise ValueError('Unknown opcode from SequenceMatcher: {}'.format(command))

    sourcefile.hash = hash