code: def test_iteration(
      scitype, mtype, fixture_index, iterate_as, iterate_cols
  ):
      """Tests __getitem__ returns pd-multiindex mtype if iterate_as="Series".
  
      Fixtures parameterized
      ----------------------
      scitype : str - scitype of fixture
      mtype : str - mtype of fixture
      fixture_index : int - index of fixture tuple with that scitype and mtype
      iterate_as : str - level on which to iterate over
      iterate_cols : bool - whether to iterate over columns
      """
      # escape for the invalid combinations, see above
      if not _is_valid_iterate_as(scitype, iterate_as):
          return None
  
      # retrieve fixture for checking
      fixture = get_examples(mtype=mtype, as_scitype=scitype).get(
          fixture_index
      )
  
      # construct VectorizedDF - we've tested above that this works
      X_vect = VectorizedDF(
          X=fixture,
          iterate_as=iterate_as,
          is_scitype=None,
          iterate_cols=iterate_cols,
      )
  
      # testing list comprehension works with indexing
      X_iter1 = [X_vect[i] for i in range(len(X_vect))]
      assert isinstance(X_iter1, list)
  
      # testing that iterator comprehension works
      X_iter2 = [X_idx for X_idx in X_vect]
      assert isinstance(X_iter2, list)
  
      # testing that as_list method works
      X_iter3 = X_vect.as_list()
      assert isinstance(X_iter3, list)
  
      # check that these are all the same
      assert deep_equals(X_iter1, X_iter2)
      assert deep_equals(X_iter2, X_iter3)
  
imports: import numpy
  import pandas
  import pytest
  from sktime.datatypes import MTYPE_REGISTER, SCITYPE_REGISTER
  from sktime.datatypes._check import AMBIGUOUS_MTYPES, check_is_mtype
  from sktime.datatypes._examples import get_examples
  from sktime.datatypes._vectorize import VectorizedDF, _enforce_index_freq
  from sktime.utils._testing.deep_equals import deep_equals
  from sktime.utils.pandas import df_map
  from sktime.utils.parallel import _get_parallel_test_fixtures
label_desc: Use image node_id 9 for calling a global function with example usage: test_iteration(scitype, mtype, fixture_index, iterate_as, iterate_cols) and returns: None