class_docstr: Basic test case for `OperatorPool`.
class_docstr_tok: ["Basic","test","case","for","`","OperatorPool","`","."]
code: def test_shareable_pool(self):
      # Shareable operator only need one
      self._op_pool.clear()
      hub_op_id = "local/add_operator"
      op1 = self._op_pool.acquire_op(
          self._key, hub_op_id, None, {"factor": 0}, "main", False
      )
      op2 = self._op_pool.acquire_op(
          self._key, hub_op_id, None, {"factor": 0}, "main", False
      )
  
      self.assertEqual(len(self._op_pool), 1)
      self._op_pool.release_op(op1)
      self.assertEqual(len(self._op_pool), 1)
      self._op_pool.release_op(op2)
      self.assertEqual(len(self._op_pool), 1)
  
file_path: towhee/tests/unittests/runtime/test_operator_pool.py
imports: import unittest
  from towhee.operator import Operator
  from towhee.runtime.operator_manager import OperatorPool
label_desc: Use image node_id 3 for calling the TestOperatorPool obj's underlying member method code with example usage: obj.test_shareable_pool() without return types