'gets the tolerance for functions when the input is of type \'ty\''

def _get_tol(self, math_fn, ty):

    low_res = {(math.gamma, np.float64): 1e-14, (math.lgamma, np.float64): 1e-13}
    default = (1e-15 if (ty == np.float64) else 1e-06)
    return low_res.get((math_fn, ty), default)
