'Subtract an element of the ground domain from ``f``.
Examples
>>> from sympy import Poly
>>> from sympy.abc import x
>>> Poly(x + 1).sub_ground(2)
Poly(x - 1, x, domain=\'ZZ\')'

def sub_ground(f, coeff):

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