code: def test_shade_cmap_errors(agg):
      with pytest.raises(ValueError):
          tf.shade(agg.a, cmap="foo")
  
      with pytest.raises(ValueError):
          tf.shade(agg.a, cmap=[])
  
imports: from __future__ import annotations
  from io import BytesIO
  import numpy
  import xarray
  import dask.array
  import PIL
  import pytest
  import datashader.transfer_functions
  from datashader.tests.test_pandas import assert_eq_ndarray, assert_eq_xr, assert_image_close
label_desc: Use image node_id 12 for calling a global function with example usage: test_shade_cmap_errors(agg) without return types