docstr: Verify length and iterator.
docstr_tok: ["Verify","length","and","iterator","."]
code: def test_len_iter(self):
      """Verify length and iterator."""
      v1 = objax.TrainVar(jn.zeros(1))
      vshared = objax.TrainVar(jn.ones(1))
      vc1 = objax.VarCollection([("a", v1), ("b", vshared)])
      vc2 = objax.VarCollection([("c", vshared)])
      vc = vc1 + vc2
      self.assertEqual(len(vc), 3)
      self.assertEqual(len(vc.keys()), 3)
      self.assertEqual(len(vc.items()), 3)
      self.assertEqual(len(vc.values()), 3)
      self.assertEqual(len(list(vc)), 2)
  
file_path: objax/tests/var_collection.py
imports: import re
  import unittest
  import jax.numpy
  import objax
  from objax.zoo import wide_resnet
label_desc: Use image node_id 6 for calling the TestVarCollection obj's underlying member method code with example usage: obj.test_len_iter() without return types