class_docstr: Test Pipeline
class_docstr_tok: ["Test","Pipeline"]
code: def test_multi_pipe(self):
      pipe1 = Pipeline.input("a", "b").map(
          "a", "c", ops.add_operator(10)
      )
      pipe2 = pipe1.map(("b", "c"), "d", ops.sub_operator())
      pipe3 = pipe2.output("c", "d")
      c1, d1 = pipe3(1, 2).get()
      self.assertEqual(c1, 11)
      self.assertEqual(d1, -9)
  
      self.assertEqual(len(pipe1.dag), 2)
      self.assertEqual(len(pipe2.dag), 3)
      self.assertIsInstance(pipe3, RuntimePipeline)
  
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 8 for calling the TestPipeline obj's underlying member method code with example usage: obj.test_multi_pipe() without return types