code: def test_datatype():
      """Test datatypes assigned to histograms"""
      hist1, hist2, hist3 = get_histograms()
      hist0 = hg.Count()
  
      assert isinstance(None, hist0.datatype)
      assert hist1.datatype == str
      np.testing.assert_array_equal(hist2.datatype, [np.number, str])
      np.testing.assert_array_equal(
          hist3.datatype, [np.datetime64, np.number, str]
      )
  
file_path: popmon/tests/popmon/hist/test_histogram.py
imports: import histogrammar
  import numpy
  import pandas
  from popmon.hist.hist_utils import is_numeric, is_timestamp, project_on_x, project_split2dhist_on_axis, sparse_bin_centers_x, split_hist_along_first_dimension, sum_entries, sum_over_x
label_desc: Use image node_id 12 for calling a global function with example usage: test_datatype() without return types