  0.  $\on{Dext}(\mathbf{C}_{\mathcal{L}_{0}}, \mathbf{C}_{\mathcal{L}_{0}}) = \varnothing$  0.  $\on{Dext}(\mathbf{C}_{\mathcal{L}_{0}}, \mathbf{C}_{\mathcal{L}_{0}}) = \varnothing$  0.  $\on{Dext}(\mathbf{C}_{\mathcal{L}_{0}}, \mathbf{C}_{\mathcal{L}_{0}}) = \varnothing$.  