class_docstr: Test diff col size
class_docstr_tok: ["Test","diff","col","size"]
code: def test_window(self):
      p1 = Pipeline.input("a", "b")
      p2 = p1.flat_map("a", "a1", lambda x: x)
      p3 = p1.flat_map("b", "b1", lambda x: x)
      p = (
          p3.concat(p2)
          .window(("a1", "b1"), "c", 3, 3, lambda x, y: x + y)
          .output("c")
      )
      self.assertEqual(
          p([1] * 10, [2] * 20).to_list(),
          [
              [[1, 1, 1, 2, 2, 2]],
              [[1, 1, 1, 2, 2, 2]],
              [[1, 1, 1, 2, 2, 2]],
              [[1, 2, 2, 2]],
              [[2, 2, 2]],
              [[2, 2, 2]],
              [[2, 2]],
          ],
      )
  
imports: import unittest
  from towhee.operator.nop import NOPNodeOperator
  from towhee.operator import PyOperator
  from towhee.runtime.pipeline import Pipeline
  from towhee.runtime.data_queue import Empty
  from towhee.runtime import ops, register
  from towhee.runtime.runtime_pipeline import RuntimePipeline
label_desc: Use image node_id 1 for calling the TestPipelineDiffColSize obj's underlying member method code with example usage: obj.test_window() without return types