def _fromRSAComponents(cls, n, e, d=None, p=None, q=None, u=None):
        """
        Build a key from RSA numerical components.

        @type n: L{int}
        @param n: The 'n' RSA variable.

        @type e: L{int}
        @param e: The 'e' RSA variable.

        @type d: L{int} or L{None}
        @param d: The 'd' RSA variable (optional for a public key).

        @type p: L{int} or L{None}
        @param p: The 'p' RSA variable (optional for a public key).

        @type q: L{int} or L{None}
        @param q: The 'q' RSA variable (optional for a public key).

        @type u: L{int} or L{None}
        @param u: The 'u' RSA variable. Ignored, as its value is determined by
        p and q.

        @rtype: L{Key}
        @return: An RSA key constructed from the values as given.
        """
        publicNumbers = rsa.RSAPublicNumbers(e=e, n=n)
        if d is None:
            # We have public components.
            keyObject = publicNumbers.public_key(default_backend())
        else:
            privateNumbers = rsa.RSAPrivateNumbers(
                p=p,
                q=q,
                d=d,
                dmp1=rsa.rsa_crt_dmp1(d, p),
                dmq1=rsa.rsa_crt_dmq1(d, q),
                iqmp=rsa.rsa_crt_iqmp(p, q),
                public_numbers=publicNumbers,
            )
            keyObject = privateNumbers.private_key(default_backend())

        return cls(keyObject)

        Build a key from RSA numerical components.

        @type n: L{int}
        @param n: The 'n' RSA variable.

        @type e: L{int}
        @param e: The 'e' RSA variable.

        @type d: L{int} or L{None}
        @param d: The 'd' RSA variable (optional for a public key).

        @type p: L{int} or L{None}
        @param p: The 'p' RSA variable (optional for a public key).

        @type q: L{int} or L{None}
        @param q: The 'q' RSA variable (optional for a public key).

        @type u: L{int} or L{None}
        @param u: The 'u' RSA variable. Ignored, as its value is determined by
        p and q.

        @rtype: L{Key}
        @return: An RSA key constructed from the values as given.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/ssh/keys.py