def lift(x):
    """
    Lift an object of a quotient ring `R/I` to `R`.

    EXAMPLES:

    We lift an integer modulo `3`::

        sage: Mod(2,3).lift()
        2

    We lift an element of a quotient polynomial ring::

        sage: R.<x> = QQ['x']
        sage: S.<xmod> = R.quo(x^2 + 1)
        sage: lift(xmod-7)
        x - 7
    """
    try:
        return x.lift()
    except AttributeError:
        raise ArithmeticError("no lift defined.")