s $=$ DependencyScheduler$()$

s$.$add$\_$task$(\text{'}$a$\text{'},[\text{'}$b$\text{'},\text{'}$c$\text{'}])$

s$.$add$\_$task$(\text{'}$b$\text{'},[\text{'}$c$\text{'},\text{'}$e$\text{'}])$

s$.\_$check$()$

s$.$show$()$