code: def run(self, messages):
          
          if not self.args.lock:
              return
  
          format.print_line('~')
          print('Locking tests')
          print()
  
          for test in self.assignment.test_map.values():
              log.info('Locking {}'.format(test.name))
              test.lock(self._hash_fn)
docs: Responsible for locking each test.