Let $(M, \partial_{-}M, \partial_{+}M)$ be a decorated 3-cobordism, where $M$ be a (topological) 3-manifold and $\partial M=-\partial_{-}M \cup \partial_{+}M$. (decorated in a sense of Turaev, Quantum invariants of knots and 3-anifold, on page 159.) Suppose $M$ is homeomorphic to a cylinder over a torus $\Sigma \times I$, where $\Sigma$ is a torus $S^1 \times S^1$. Let $f_{-}: \Sigma \to \partial_{-}M$ and $f_{+}: \Sigma \to \partial_{+}M$ be parametrizations of bottom and top boundaries respectively. Consider the composition $H_1(\Sigma; \mathbb{Z}) \to H_1(\partial_{-}M; \mathbb{Z}) \to H_1(\partial_{+}M; \mathbb{Z}) \to H_1(\Sigma; \mathbb{Z})$. Here the first and the third ismorphism are induced by the parametrizations $f_{\pm}$ respectively and the second isomorphism (let's say $h$) is obtained by pushing loops in the bottom base of $M$ to the top base using the cylindrical structure on $M$. **Question** Is this cobordism $(M, \partial_{-}M, \partial_{+}M)$ (d-)homeomorphic to a cobordims $(\Sigma \times I, \Sigma \times 0, \Sigma \times 1)$, where the parametrization on the top is given by the identity of $\Sigma$ and the bottom is given by $f_{+}^{-1}hf_{-}$? Please give me a proof. Thanks.