code: def check_dependencies(self):
          
          deadlocks = []
  
          for task in self.iflat_tasks():
              for dep in task.deps:
                  if dep.node.depends_on(task):
                      deadlocks.append((task, dep.node))
  
          if deadlocks:
              lines = ["Detect wrong list of dependecies that will lead to a deadlock:"]
              lines.extend(["%s <--> %s" % nodes for nodes in deadlocks])
              raise RuntimeError("\n".join(lines))
docs: Test the dependencies of the nodes for possible deadlocks.