class_docstr: Test Pipeline
class_docstr_tok: ["Test","Pipeline"]
code: def test_callable_class(self):
      class CallableClass:
          def __init__(self, x):
              self._x = x
  
          def __call__(self, x):
              return self._x + x
  
      pipe = (
          Pipeline.input("a")
          .map("a", "c", CallableClass(2))
          .output("c")
      )
      res = pipe(1).get()
      self.assertEqual(res[0], 3)
  
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 4 for calling the TestPipeline obj's underlying member method code with example usage: obj.test_callable_class() and returns: unknown