How to use the mutmut.cache.SourceFile 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':

def register_mutants(mutations_by_file):
    for filename, mutation_ids in mutations_by_file.items():
        hash = hash_of(filename)
        sourcefile = get_or_create(SourceFile, filename=filename)
        if hash == sourcefile.hash:
            continue

        for mutation_id in mutation_ids:
            line = Line.get(sourcefile=sourcefile, line=mutation_id.line, line_number=mutation_id.line_number)
            if line is None:
                raise ValueError("Obtained null line for mutation_id: {}".format(mutation_id))
            get_or_create(Mutant, line=line, index=mutation_id.index, defaults=dict(status=UNTESTED))

        sourcefile.hash = hash

NO_TESTS_FOUND = 'NO TESTS FOUND'


class MiscData(db.Entity):
    key = PrimaryKey(str, auto=True)
    value = Optional(str, autostrip=False)


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: