How to use the pgpy.packet.types.MPI function in PGPy

from datetime import datetime
    from enum import Enum

    # do some type checking to determine if we should check the identity of an object member
    # these types are singletons
    if isinstance(obj, (Enum, bool, type(None))):
        return False

    # these types are immutable
    if isinstance(obj, (six.string_types, datetime)):
        return False

    # integers are kind of a special case.
    #   ints that do not exceed sys.maxsize are singletons, and in either case are immutable
    #   this shouldn't apply to MPIs, though, which are subclasses of int
    if isinstance(obj, int) and not isinstance(obj, pgpy.packet.types.MPI):
        return False

    return True

def clear(self):
        """delete and re-initialize all private components to zero"""
        for field in self.__privfields__:
            delattr(self, field)
            setattr(self, field, MPI(0))

padder = PKCS7(64).padder()
        m = padder.update(_m) + padder.finalize()

        km = pk.keymaterial
        ct = cls()

        # generate ephemeral key pair and keep public key in ct
        # use private key to compute the shared point "s"
        if km.oid == EllipticCurveOID.Curve25519:
            v = x25519.X25519PrivateKey.generate()
            x = v.public_key().public_bytes(encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw)
            ct.p = ECPoint.from_values(km.oid.key_size, ECPointFormat.Native, x)
            s = v.exchange(km.__pubkey__())
        else:
            v = ec.generate_private_key(km.oid.curve(), default_backend())
            x = MPI(v.public_key().public_numbers().x)
            y = MPI(v.public_key().public_numbers().y)
            ct.p = ECPoint.from_values(km.oid.key_size, ECPointFormat.Standard, x, y)
            s = v.exchange(ec.ECDH(), km.__pubkey__())

        # derive the wrapping key
        z = km.kdf.derive_key(s, km.oid, PubKeyAlgorithm.ECDH, pk.fingerprint)

        # compute C
        ct.c = aes_key_wrap(z, m, default_backend())

        return ct

def _generate(self, key_size):
        if any(c != 0 for c in self):  # pragma: no cover
            raise PGPError("key is already populated")

        # generate some big numbers!
        pk = rsa.generate_private_key(65537, key_size, default_backend())
        pkn = pk.private_numbers()

        self.n = MPI(pkn.public_numbers.n)
        self.e = MPI(pkn.public_numbers.e)
        self.d = MPI(pkn.d)
        self.p = MPI(pkn.p)
        self.q = MPI(pkn.q)
        # from the RFC:
        # "- MPI of u, the multiplicative inverse of p, mod q."
        # or, simply, p^-1 mod p
        # rsa.rsa_crt_iqmp(p, q) normally computes q^-1 mod p,
        # so if we swap the values around we get the answer we want
        self.u = MPI(rsa.rsa_crt_iqmp(pkn.q, pkn.p))

        del pkn
        del pk

        self._compute_chksum()

# generate some big numbers!
        pk = rsa.generate_private_key(65537, key_size, default_backend())
        pkn = pk.private_numbers()

        self.n = MPI(pkn.public_numbers.n)
        self.e = MPI(pkn.public_numbers.e)
        self.d = MPI(pkn.d)
        self.p = MPI(pkn.p)
        self.q = MPI(pkn.q)
        # from the RFC:
        # "- MPI of u, the multiplicative inverse of p, mod q."
        # or, simply, p^-1 mod p
        # rsa.rsa_crt_iqmp(p, q) normally computes q^-1 mod p,
        # so if we swap the values around we get the answer we want
        self.u = MPI(rsa.rsa_crt_iqmp(pkn.q, pkn.p))

        del pkn
        del pk

        self._compute_chksum()

def parse(self, packet):
        super(RSAPriv, self).parse(packet)
        self.s2k.parse(packet)

        if not self.s2k:
            self.d = MPI(packet)
            self.p = MPI(packet)
            self.q = MPI(packet)
            self.u = MPI(packet)

            if self.s2k.usage == 0:
                self.chksum = packet[:2]
                del packet[:2]

        else:
            ##TODO: this needs to be bounded to the length of the encrypted key material
            self.encbytes = packet

def parse(self, packet):
        super(ElGPriv, self).parse(packet)
        self.s2k.parse(packet)

        if not self.s2k:
            self.x = MPI(packet)

        else:
            self.encbytes = packet

        if self.s2k.usage in [0, 255]:
            self.chksum = packet[:2]
            del packet[:2]

def decrypt_keyblob(self, passphrase):
        kb = super(EdDSAPriv, self).decrypt_keyblob(passphrase)
        del passphrase
        self.s = MPI(kb)

def parse(self, packet):
        super(RSAPriv, self).parse(packet)
        self.s2k.parse(packet)

        if not self.s2k:
            self.d = MPI(packet)
            self.p = MPI(packet)
            self.q = MPI(packet)
            self.u = MPI(packet)

            if self.s2k.usage == 0:
                self.chksum = packet[:2]
                del packet[:2]

        else:
            ##TODO: this needs to be bounded to the length of the encrypted key material
            self.encbytes = packet

def from_signer(self, sig):
        seq, _ = decoder.decode(sig)
        self.r = MPI(seq[0])
        self.s = MPI(seq[1])