def tuple_to_sympy(t, x, y):
d = dict(t)
nvars = len(t[0][0])
if nvars == 1:
return Poly.from_dict(d, x, domain='QQ')
elif nvars == 2:
return Poly.from_dict(d, x, y, domain='QQ')
else:
raise ValueError("Expected univariate or bivariate expression")
