How to use the rsa.common function in rsa

def encrypt(text, pub_key):
    block_size = rsa.common.byte_size(pub_key.n) - 11
    encrypted = ""
    for part in split_len(text, block_size):
        encrypted += rsa.encrypt(part, pub_key)
    return encrypted

:raise OverflowError: when the message is too large to fit in the padded
        block.

    >>> from rsa import key, common
    >>> (pub_key, priv_key) = key.newkeys(256)
    >>> message = b'hello'
    >>> crypto = encrypt(message, pub_key)

    The crypto text should be just as long as the public key 'n' component:

    >>> len(crypto) == common.byte_size(pub_key.n)
    True

    """

    keylength = common.byte_size(pub_key.n)
    padded = _pad_for_encryption(message, keylength)

    payload = transform.bytes2int(padded)
    encrypted = core.encrypt_int(payload, pub_key.e, pub_key.n)
    block = transform.int2bytes(encrypted, keylength)

    return block

def randint(maxvalue):
    """Returns a random integer x with 1 <= x <= maxvalue

    May take a very long time in specific situations. If maxvalue needs N bits
    to store, the closer maxvalue is to (2 ** N) - 1, the faster this function
    is.
    """

    bit_size = common.bit_size(maxvalue)

    tries = 0
    while True:
        value = read_random_int(bit_size)
        if value <= maxvalue:
            break

        if tries and tries % 10 == 0:
            # After a lot of tries to get the right number of bits but still
            # smaller than maxvalue, decrease the number of bits by 1. That'll
            # dramatically increase the chances to get a large enough number.
            bit_size -= 1
        tries += 1

    return value

:raise OverflowError: if the private key is too small to contain the
        requested hash.

    """

    # Get the ASN1 code for this hash method
    if hash not in HASH_ASN1:
        raise ValueError('Invalid hash method: %s' % hash)
    asn1code = HASH_ASN1[hash]

    # Calculate the hash
    hash = _hash(message, hash)

    # Encrypt the hash with the private key
    cleartext = asn1code + hash
    keylength = common.byte_size(priv_key.n)
    padded = _pad_for_signing(cleartext, keylength)

    payload = transform.bytes2int(padded)
    encrypted = priv_key.blinded_encrypt(payload)
    block = transform.int2bytes(encrypted, keylength)

    return block

def decrypt(encrypted, pri_key):
    block_size = rsa.common.byte_size(pri_key.n)
    text = ""
    for part in split_len(encrypted, block_size):
        text += rsa.decrypt(part, pri_key)
    return text

def unblind(self, blinded: int, r: int) -> int:
        """Performs blinding on the message using random number 'r'.

        :param blinded: the blinded message, as integer, to unblind.
        :param r: the random number to unblind with.
        :return: the original message.

        The blinding is such that message = unblind(decrypt(blind(encrypt(message))).

        See https://en.wikipedia.org/wiki/Blinding_%28cryptography%29
        """

        return (rsa.common.inverse(r, self.n) * blinded) % self.n

self.p = p
        self.q = q

        # Calculate the other values if they aren't supplied
        if exp1 is None:
            self.exp1 = int(d % (p - 1))
        else:
            self.exp1 = exp1

        if exp1 is None:
            self.exp2 = int(d % (q - 1))
        else:
            self.exp2 = exp2

        if coef is None:
            self.coef = rsa.common.inverse(q, p)
        else:
            self.coef = coef

:param hash_method: the hash method used on the message. Use 'MD5', 'SHA-1',
        'SHA-224', SHA-256', 'SHA-384' or 'SHA-512'.
    :return: a message signature block.
    :raise OverflowError: if the private key is too small to contain the
        requested hash.

    """

    # Get the ASN1 code for this hash method
    if hash_method not in HASH_ASN1:
        raise ValueError('Invalid hash method: %s' % hash_method)
    asn1code = HASH_ASN1[hash_method]

    # Encrypt the hash with the private key
    cleartext = asn1code + hash_value
    keylength = common.byte_size(priv_key.n)
    padded = _pad_for_signing(cleartext, keylength)

    payload = transform.bytes2int(padded)
    encrypted = priv_key.blinded_encrypt(payload)
    block = transform.int2bytes(encrypted, keylength)

    return block

self.p = p
        self.q = q

        # Calculate the other values if they aren't supplied
        if exp1 is None:
            self.exp1 = int(d % (p - 1))
        else:
            self.exp1 = exp1

        if exp2 is None:
            self.exp2 = int(d % (q - 1))
        else:
            self.exp2 = exp2

        if coef is None:
            self.coef = rsa.common.inverse(q, p)
        else:
            self.coef = coef

bytes than fit into the block.
    '''
    # Type checking
    if not is_integer(number):
        raise TypeError("You must pass an integer for 'number', not %s" %
            number.__class__)

    if number < 0:
        raise ValueError('Negative numbers cannot be used: %i' % number)

    # Do some bounds checking
    if number == 0:
        needed_bytes = 1
        raw_bytes = [ZERO_BYTE]
    else:
        needed_bytes = common.byte_size(number)
        raw_bytes = []

    # You cannot compare None > 0 in Python 3x. It will fail with a TypeError.
    if block_size and block_size > 0:
        if needed_bytes > block_size:
            raise OverflowError('Needed %i bytes for number, but block size '
                'is %i' % (needed_bytes, block_size))

    # Convert the number to bytes.
    while number > 0:
        raw_bytes.insert(0, byte(number & 0xFF))
        number >>= 8

    # Pad with zeroes to fill the block
    if block_size and block_size > 0:
        padding = (block_size - needed_bytes) * ZERO_BYTE