How to use the mutagen.mp4.MP4Cover function in mutagen

def test_covr_blank_format(self):
        data = Atom.render(b"data", b"\x00\x00\x00\x00" + b"\x00" * 4 + b"whee")
        covr = Atom.render(b"covr", data)
        tags = self.wrap_ilst(covr)
        self.failUnlessEqual(MP4Cover.FORMAT_JPEG, tags[b"covr"][0].imageformat)

def test_cover_png(self):
        self.set_key('covr', [
            MP4Cover(b'woooo', MP4Cover.FORMAT_PNG),
            MP4Cover(b'hoooo', MP4Cover.FORMAT_JPEG),
        ])

def __parse_cover(self, atom, data):
        self[atom.name] = []
        pos = 0
        while pos < atom.length - 8:
            length, name, imageformat = struct.unpack(">I4sI",
                                                      data[pos:pos+12])
            if name != b"data":
                if name == b"name":
                    pos += length
                    continue
                raise MP4MetadataError(
                    "unexpected atom %r inside 'covr'" % name)
            if imageformat not in (MP4Cover.FORMAT_JPEG, MP4Cover.FORMAT_PNG):
                imageformat = MP4Cover.FORMAT_JPEG
            cover = MP4Cover(data[pos+16:pos+length], imageformat)
            self[atom.name].append(cover)
            pos += length

def pic_to_bin(image):
    data = image[util.DATA]
    mime = imghdr.what(None, data)
    if mime == 'png':
        format = MP4Cover.FORMAT_PNG
    elif mime == 'jpeg':
        format = MP4Cover.FORMAT_JPEG
    else:
        return
    return MP4Cover(data, format)

def __fixed_render_cover(self, key, value):
        atom_data = []
        for cover in value:
            try:
                imageformat = cover.imageformat
            except AttributeError:
                imageformat = MP4Cover.FORMAT_JPEG
            atom_data.append(Atom.render(
                b"data", struct.pack(">2I", imageformat, 0) + bytes(cover)))
        return Atom.render(_key2name(key), b"".join(atom_data))

tags["trkn"] = [(int(metadata["tracknumber"]),
                                 int(metadata["totaltracks"]))]
            else:
                tags["trkn"] = [(int(metadata["tracknumber"]), 0)]

        if "discnumber" in metadata:
            if "totaldiscs" in metadata:
                tags["disk"] = [(int(metadata["discnumber"]),
                                 int(metadata["totaldiscs"]))]
            else:
                tags["disk"] = [(int(metadata["discnumber"]), 0)]

        covr = []
        for image in metadata.images.to_be_saved_to_tags():
            if image.mimetype == "image/jpeg":
                covr.append(MP4Cover(image.data, MP4Cover.FORMAT_JPEG))
            elif image.mimetype == "image/png":
                covr.append(MP4Cover(image.data, MP4Cover.FORMAT_PNG))
        if covr:
            tags["covr"] = covr

        self._remove_deleted_tags(metadata, tags)

        file.save()

def serialize(self, image):
        if image.mime_type == 'image/png':
            kind = mutagen.mp4.MP4Cover.FORMAT_PNG
        elif image.mime_type == 'image/jpeg':
            kind = mutagen.mp4.MP4Cover.FORMAT_JPEG
        else:
            raise ValueError('MP4 files only supports PNG and JPEG images')
        return mutagen.mp4.MP4Cover(image.data, kind)

def serialize(self, image):
        if image.mime_type == 'image/png':
            kind = mutagen.mp4.MP4Cover.FORMAT_PNG
        elif image.mime_type == 'image/jpeg':
            kind = mutagen.mp4.MP4Cover.FORMAT_JPEG
        else:
            raise ValueError('MP4 files only supports PNG and JPEG images')
        return mutagen.mp4.MP4Cover(image.data, kind)