1. edu
   1. edu.umass
      1. edu.umass.cs
         1. edu.umass.cs.cs691f
            1. (trait)HasSym
            2. (object)(trait)Subst
            3. (object)(trait)Sym
            4. (object)
               Unification
            5. (case class)UnifyException
            1. edu.umass.cs.cs691f.hw
               1. edu.umass.cs.cs691f.hw.backtrack
                  1. (trait)SearchLike