class_docstr: DataQueue test
code: def test_scalar_with_empty_ques(self):
      que = DataQueue(
          [("url", ColumnType.SCALAR), ("vec", ColumnType.QUEUE)]
      )
      que.put(("http://towhee.io", Empty()))
      self.assertEqual(que.size, 0)
      que.seal()
      self.assertEqual(que.size, 1)
      self.assertEqual(que.to_list(), [["http://towhee.io", Empty()]])
  
imports: import unittest
  import threading
  import time
  from functools import partial
  from towhee.runtime.data_queue import DataQueue, ColumnType, Empty
label_desc: Use image node_id 21 for calling the TestDataQueue obj's underlying member method code with example usage: obj.test_scalar_with_empty_ques() without return types