code: def test_NA_mixed_dtype():
      data_mixed = dict(
          int=[1, None, 2, 3, 1000],
          float=[None, 1.5, 2.5, 3.5, None],
          bool=[True, None, False, None, None],
          categorical=[5, 1, 5, 3, None],
          string=[None, None, None, "df protocol", None],
      )
      assert_df_unique_dtype_cols(data_mixed)
  
imports: from typing import Any, Tuple
  import cupy
  import pandas
  import pytest
  import cudf
  from cudf.core._compat import PANDAS_GE_150
  from cudf.core.buffer import as_buffer
  from cudf.core.column import as_column, build_column
  from cudf.core.df_protocol import DataFrameObject, _CuDFBuffer, _CuDFColumn, _DtypeKind, _MaskKind, _protocol_buffer_to_cudf_buffer, from_dataframe, protocol_dtype_to_cupy_dtype
  from cudf.testing._utils import assert_eq
label_desc: Use image node_id 21 for calling a global function with example usage: test_NA_mixed_dtype() without return types