'Internal one step complex root refinement procedure.'

def _inner_refine(self):

    ((u, v), (s, t)) = (self.a, self.b)
    (I, Q) = (self.I, self.Q)
    (f1, F1) = (self.f1, self.F1)
    (f2, F2) = (self.f2, self.F2)
    dom = self.dom
    if ((s - u) > (t - v)):
        (D_L, D_R) = _vertical_bisection(1, (u, v), (s, t), I, Q, F1, F2, f1, f2, dom)
        if (D_L[0] == 1):
            (_, a, b, I, Q, F1, F2) = D_L
        else:
            (_, a, b, I, Q, F1, F2) = D_R
    else:
        (D_B, D_U) = _horizontal_bisection(1, (u, v), (s, t), I, Q, F1, F2, f1, f2, dom)
        if (D_B[0] == 1):
            (_, a, b, I, Q, F1, F2) = D_B
        else:
            (_, a, b, I, Q, F1, F2) = D_U
    return ComplexInterval(a, b, I, Q, F1, F2, f1, f2, dom, self.conj)
