'Add an element of the ground domain to ``f``.
Examples
>>> from sympy import Poly
>>> from sympy.abc import x
>>> Poly(x + 1).add_ground(2)
Poly(x + 3, x, domain=\'ZZ\')'

def add_ground(f, coeff):

    if hasattr(f.rep, 'add_ground'):
        result = f.rep.add_ground(coeff)
    else:
        raise OperationNotSupported(f, 'add_ground')
    return f.per(result)
