class_docstr: TestDataLoader
code: def test_local_ops(self):
      size = 100
      p = (
          pipe.input("num")
          .map("num", "ret", lambda x: x + 1)
          .output("ret")
      )
      expect = list(range(1, size + 1))
      for i, data in enumerate(
          DataLoader(
              ops.local.data_source_op(size), parser=lambda x: x[1]
          )
      ):
          self.assertEqual(p(data).to_list()[0][0], expect[i])
  
      res = []
      for data in DataLoader(
          ops.local.data_source_op(size),
          parser=lambda x: x[1],
          batch_size=7,
      ):
          for ret in p.batch(data):
              res.append(ret.to_list()[0][0])
      self.assertEqual(res, expect)
  
imports: import unittest
  from towhee import DataLoader, pipe, ops, register
  from towhee.operator.base import PyOperator
label_desc: Use image node_id 3 for calling the TestDataLoader obj's underlying member method code with example usage: obj.test_local_ops() without return types