'Construct an RSA key from a tuple of valid RSA components.
The modulus **n** must be the product of two primes.
The public exponent **e** must be odd and larger than 1.
In case of a private key, the following equations must apply:
- e != 1
- p*q = n
- e*d = 1 mod (p-1)(q-1)
- p*u = 1 mod q
:Parameters:
tup : tuple
A tuple of long integers, with at least 2 and no
more than 6 items. The items come in the following order:
1. RSA modulus (n).
2. Public exponent (e).
3. Private exponent (d). Only required if the key is private.
4. First factor of n (p). Optional.
5. Second factor of n (q). Optional.
6. CRT coefficient, (1/p) mod q (u). Optional.
:Return: An RSA key object (`_RSAobj`).'

def construct(self, tup):

    key = self._math.rsa_construct(*tup)
    return _RSAobj(self, key)
