code: def no_next_candidate(self):
          
          while self.candidates:
              candidates = self.candidates
              self.candidates = []
              self.will_not_build(candidates)
          return None
docs: Stops Taskmaster processing by not returning a next candidate.
  
          Note that we have to clean-up the Taskmaster candidate list
          because the cycle detection depends on the fact all nodes have
          been processed somehow.