class_docstr: Test Pipeline
class_docstr_tok: ["Test","Pipeline"]
code: def test_property(self):
      pipe1 = Pipeline.input("a", "b").map(
          "a", "c", ops.towhee.test_op1("a")
      )
      self.assertEqual(len(pipe1.dag), 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 TestPipeline obj's underlying member method code with example usage: obj.test_property() without return types