state transitions cluster__d d cluster__d_e e cluster__a a cluster__a_b b __initial __initial->_a _d_initial _d_initial->_d_e _d_e_initial _d_e_f f enter ^out.done _d_e_initial->_d_e_f _a_initial _a_initial->_a_b _a_b_initial _a_b_c c _a_b_initial->_a_b_c _a_b_c->_d_e_f