code: def test_dataset_1_column_nulls():
      # Arrange
      data = {
          "col1": ["foo", "bar", "null"],
          "col2": ["foo", "bar", 1],
          "col3": [1, 2, 3],
      }
      dataframe = pd.DataFrame(data=data)
      # Act
      result = MixedNulls().run(dataframe)
      # Assert
      assert_that(
          result.value["columns"],
          has_entries(
              col1=has_length(1), col2=equal_to({}), col3=equal_to({})
          ),
      )
  
imports: import numpy
  import pandas
  from hamcrest import any_of, assert_that, calling, close_to, equal_to, greater_than, has_entries, has_entry, has_items, has_length, is_, raises
  from deepchecks.core.errors import DatasetValidationError, DeepchecksValueError
  from deepchecks.tabular.checks.data_integrity.mixed_nulls import MixedNulls
  from deepchecks.tabular.dataset import Dataset
  from tests.base.utils import equal_condition_result
label_desc: Use image node_id 18 for calling a global function with example usage: test_dataset_1_column_nulls() without return types