     C_0+iC_0(z-0)^{\frac00}-C_0(z-0)-iC_0(z-0)^{\frac00}+{\mathcal{O}}(z-0)^0, & \hbox{${\mathrm{Im}\,}z<0$,}                    \end{array}                  \right.$$ and $$\lambda_0(z)=\left\{                    \begin{array}{ll}                      C_0+iC_0(z-0)^{\frac00}-C_0(z-0)-iC_0(z-0)^{\frac00}+{\mathcal{O}}(z-0)^0, & \hbox{${\mathrm{Im}\,}z>0$,} \\                      C_0-iC_0(z-0)^{\frac00}-C_0(z-0)+iC_0(z-0)^{\frac00}+{\mathcal{O}}(z-0)^0, & \hbox{${\mathrm{Im}\,}z<0$,}                    \end{array}                  \right.$$ 