class_docstr: Test DataVisualizer base class
class_docstr_tok: ["Test","DataVisualizer","base","class"]
code: def assert_not_fitted(self, obj):
      __tracebackhide__ = True
      for field in self.FIELDS:
          if field.endswith("_"):
              assert not hasattr(
                  obj, field
              ), "has {} before fit".format(field)
          else:
              msg = "missing internal var {}".format(field)
              assert getattr(obj, field) is None, msg
  
imports: import pytest
  import numpy
  import numpy.testing
  from tests.fixtures import Dataset
  from yellowbrick.base import Visualizer
  from yellowbrick.features.base import *
  from sklearn.base import BaseEstimator, TransformerMixin
  from sklearn.datasets import make_classification, make_regression
  from unittest.mock import Mock
label_desc: Use image node_id 1 for calling the TestDataVisualizer obj's underlying member method code with example usage: obj.assert_not_fitted(obj) without return types