code: private ClassVertex resolveClassVertex(ClassDescriptor classDescriptor) throws ClassNotFoundException {
          ClassVertex typeVertex = optionallyResolveClassVertex(classDescriptor);
  
          if (!typeVertex.isResolved()) {
              ClassDescriptor.throwClassNotFoundException(classDescriptor);
          }
  
          assert typeVertex.isResolved();
          return typeVertex;
      }
docs: Resolve a class named by given ClassDescriptor and return its resolved
  ClassVertex.
  
  @param classDescriptor
  a ClassDescriptor
  @return resolved ClassVertex representing the class in the
  InheritanceGraph
  @throws ClassNotFoundException
  if the class named by the ClassDescriptor does not exist