code: def testGettingItems(self):
      print("\n**** Getting the data by label test ****\n")
  
      dim = 16
      num_elements = 10000
  
      # Generating sample data
      data = np.float32(np.random.random((num_elements, dim)))
      labels = np.arange(0, num_elements)
  
      # Declaring index
      p = hnswlib.Index(
          space="l2", dim=dim
      )  # possible options are l2, cosine or ip
  
      # Initiating index
      # max_elements - the maximum number of elements, should be known beforehand
      #     (probably will be made optional in the future)
      #
      # ef_construction - controls index search speed/build speed tradeoff
      # M - is tightly connected with internal dimensionality of the data
      #     strongly affects the memory consumption
  
      p.init_index(max_elements=num_elements, ef_construction=100, M=16)
  
      # Controlling the recall by setting ef:
      # higher ef leads to better accuracy, but slower search
      p.set_ef(100)
  
      p.set_num_threads(4)  # by default using all available cores
  
      # Before adding anything, getting any labels should fail
      self.assertRaises(Exception, lambda: p.get_items(labels))
  
      print("Adding all elements (%d)" % (len(data)))
      p.add_items(data, labels)
  
      # Getting data by label should raise an exception if a scalar is passed:
      self.assertRaises(ValueError, lambda: p.get_items(labels[0]))
  
      # After adding them, all labels should be retrievable
      returned_items_np = p.get_items(labels)
      self.assertTrue((data == returned_items_np).all())
  
      # check returned type of get_items
      self.assertTrue(isinstance(returned_items_np, np.ndarray))
      returned_items_list = p.get_items(labels, return_type="list")
      self.assertTrue(isinstance(returned_items_list, list))
      self.assertTrue(isinstance(returned_items_list[0], list))
  
imports: import unittest
  import numpy
  import hnswlib
label_desc: Use image node_id 1 for calling the RandomSelfTestCase obj's underlying member method code with example usage: obj.testGettingItems() without return types