E[true~U (s_0\wedge EX(E[\neg s_0 U (s_0\wedge\neg s_0)]\vee EG\neg s_0))]$$ is processed by $HandleCTL$ from bottom to up as follows.  0.  the atomic subformula $s_0$ is processed by $HandleCTL$, and a labeling function $L_0=\{(s_0,0)\}$ is returned;  0.  the atomic subformula $s_0$ is processed, and a labeling function $L_0=\{(s_0,0)\}$ is returned;  0.  to process $\neg s_0$, $HandleNegation$ is called with $L_0$ to return a labeling function $L_0=\{(s_0,0),(s_0,0),(s_0,0),(s_0,0)\}$;  0.  to process $