How to use the umbral.keys.UmbralPublicKey.from_bytes function in umbral

def test_kfrags():

    vector_file = os.path.join('vectors', 'vectors_kfrags.json')
    try:
        with open(vector_file) as f:
            vector_suite = json.load(f)
    except OSError:
        raise

    verifying_key = UmbralPublicKey.from_bytes(bytes.fromhex(vector_suite['verifying_key']))
    delegating_key = UmbralPublicKey.from_bytes(bytes.fromhex(vector_suite['delegating_key']))
    receiving_key = UmbralPublicKey.from_bytes(bytes.fromhex(vector_suite['receiving_key']))

    for json_kfrag in vector_suite['vectors']:
        kfrag = KFrag.from_bytes(bytes.fromhex(json_kfrag['kfrag']))
        assert kfrag.verify(signing_pubkey=verifying_key,
                            delegating_pubkey=delegating_key,
                            receiving_pubkey=receiving_key), \
            'Invalid KFrag {}'.format(kfrag.to_bytes().hex())

def test_public_key_serialization(random_ec_curvebn1):
    priv_key = random_ec_curvebn1

    params = default_params()
    pub_key = priv_key * params.g

    umbral_key = UmbralPublicKey(pub_key, params)

    encoded_key = umbral_key.to_bytes()

    decoded_key = UmbralPublicKey.from_bytes(encoded_key)
    assert pub_key == decoded_key.point_key

def test_kfrags():

    vector_file = os.path.join('vectors', 'vectors_kfrags.json')
    try:
        with open(vector_file) as f:
            vector_suite = json.load(f)
    except OSError:
        raise

    verifying_key = UmbralPublicKey.from_bytes(bytes.fromhex(vector_suite['verifying_key']))
    delegating_key = UmbralPublicKey.from_bytes(bytes.fromhex(vector_suite['delegating_key']))
    receiving_key = UmbralPublicKey.from_bytes(bytes.fromhex(vector_suite['receiving_key']))

    for json_kfrag in vector_suite['vectors']:
        kfrag = KFrag.from_bytes(bytes.fromhex(json_kfrag['kfrag']))
        assert kfrag.verify(signing_pubkey=verifying_key,
                            delegating_pubkey=delegating_key,
                            receiving_pubkey=receiving_key), \
            'Invalid KFrag {}'.format(kfrag.to_bytes().hex())

def get_users_public_keys(name, serialized=False):
    dirname = "accounts/" + name + "/"
    fname = dirname+"recipent.public.json"
    with open(fname) as data_file:    
        data = json.load(data_file)
    enc_pubkey = UmbralPublicKey.from_bytes(bytes.fromhex(data["enc"]))
    sig_pubkey = UmbralPublicKey.from_bytes(bytes.fromhex(data["sig"]))
    print(enc_pubkey, sig_pubkey)
    if serialized:
        return (base58.b58encode(bytes.fromhex(data["enc"])).decode("utf-8"),
         base58.b58encode(bytes.fromhex(data["sig"])).decode("utf-8"))
    return (enc_pubkey, sig_pubkey)

def grant_others_access(self, username, password, cid, label, recp_enc_b58_key, recp_sig_b58_key):
        alice = self.act_as_alice(username, password)    
        enc = UmbralPublicKey.from_bytes(base58.b58decode(recp_enc_b58_key))
        sig = UmbralPublicKey.from_bytes(base58.b58decode(recp_sig_b58_key))
        nucid = creat_nucid(alice, cid, enc, sig, label.encode("utf-8"))
        return nucid

def grant_others_access(self, username, password, cid, label, recp_enc_b58_key, recp_sig_b58_key):
        alice = self.act_as_alice(username, password)    
        enc = UmbralPublicKey.from_bytes(base58.b58decode(recp_enc_b58_key))
        sig = UmbralPublicKey.from_bytes(base58.b58decode(recp_sig_b58_key))
        nucid = creat_nucid(alice, cid, enc, sig, label.encode("utf-8"))
        return nucid

def get_users_public_keys(name, serialized=False):
    dirname = "accounts/" + name + "/"
    fname = dirname+"recipent.public.json"
    with open(fname) as data_file:    
        data = json.load(data_file)
    enc_pubkey = UmbralPublicKey.from_bytes(bytes.fromhex(data["enc"]))
    sig_pubkey = UmbralPublicKey.from_bytes(bytes.fromhex(data["sig"]))
    print(enc_pubkey, sig_pubkey)
    if serialized:
        return (base58.b58encode(bytes.fromhex(data["enc"])).decode("utf-8"),
         base58.b58encode(bytes.fromhex(data["sig"])).decode("utf-8"))
    return (enc_pubkey, sig_pubkey)

def decrypt(self, bob, item_cid, pol, sig, lab):
        policy_pubkey = UmbralPublicKey.from_bytes(bytes.fromhex(pol))
        alices_sig_pubkey = UmbralPublicKey.from_bytes(bytes.fromhex(sig))
        label = lab.encode()
        dat = self.ipfs_gateway_api.cat(item_cid)
        doctor = bob
        doctor.join_policy(label, alices_sig_pubkey)
        data = msgpack.loads(dat, raw=False)
        message_kits = (UmbralMessageKit.from_bytes(k) for k in data['kits'])
        data_source = Enrico.from_public_keys(
            {SigningPower: data['data_source']},
            policy_encrypting_key=policy_pubkey
        )
        message_kit = next(message_kits)
        start = timer()
        retrieved_plaintexts = doctor.retrieve(
            label=label,
            message_kit=message_kit,