class_docstr: Base class for MissingDataVisualizers.
      
code: def get_feature_names(self):
      if self.features_ is None:
          return [
              "Feature {}".format(str(n))
              for n in np.arange(len(self.features_))
          ]
      return self.features_
  
imports: import numpy
  from yellowbrick.features.base import DataVisualizer
  from yellowbrick.utils import is_dataframe
label_desc: Use image node_id 2 for calling the MissingDataVisualizer obj's underlying member method code with example usage: obj.get_feature_names() and returns: self, unknown