code: def test__is_polars_df():
      """Check that _is_polars_df return False for non-dataframe objects."""
  
      class LooksLikePolars:
          def __init__(self):
              self.columns = ["a", "b"]
              self.schema = ["a", "b"]
  
      assert not _is_polars_df(LooksLikePolars())
  
imports: import string
  import timeit
  import warnings
  from copy import copy
  from itertools import chain
  import numpy
  import pytest
  from sklearn import config_context
  from sklearn.utils import _approximate_mode, _determine_key_type, _get_column_indices, _is_polars_df, _message_with_time, _print_elapsed_time, _safe_assign, _safe_indexing, _to_object_array, check_random_state, column_or_1d, deprecated, gen_even_slices, get_chunk_n_rows, is_scalar_nan, resample, safe_mask, shuffle
  from sklearn.utils._mocking import MockDataFrame
  from sklearn.utils._testing import _convert_container, assert_allclose_dense_sparse, assert_array_equal, assert_no_warnings
  from sklearn.utils.fixes import CSC_CONTAINERS, CSR_CONTAINERS
label_desc: Use image node_id 45 for calling a global function with example usage: test__is_polars_df() without return types