old_contents: import numpy as np
  import scipy.stats.stats as stat
  
  from laserchicken.feature_extractor.abc import FeatureExtractor
  from laserchicken.keys import point
  
  
  class RangeZFeatureExtractor(FeatureExtractor):
      """Calculates the max, min and range and max on the z axis."""
  
      DEFAULT_MAX = float('NaN')
      DEFAULT_MIN = float('NaN')
      DATA_KEY = 'z'
  
      @classmethod
      def requires(cls):
          return []
  
      @classmethod
      def provides(cls):
          return ['max_z', 'min_z', 'range_z']
  
      def extract(self, source_point_cloud, neighborhood, target_point_cloud, target_index, volume_description):
          if neighborhood:
              z = source_point_cloud[point][self.DATA_KEY]['data'][neighborhood]
              max_z = np.max(z) if len(z) > 0 else self.DEFAULT_MAX
              min_z = np.min(z) if len(z) > 0 else self.DEFAULT_MIN
              range_z = max_z - min_z
          else:
              max_z = min_z = range_z = np.NaN
          return max_z, min_z, range_z
  
new_contents: import numpy as np
  
  from laserchicken.feature_extractor.abc import FeatureExtractor
  from laserchicken.keys import point
  
  
  class RangeZFeatureExtractor(FeatureExtractor):
      """Calculates the max, min and range on the z axis."""
  
      DEFAULT_MAX = float('NaN')
      DEFAULT_MIN = float('NaN')
      DATA_KEY = 'z'
  
      @classmethod
      def requires(cls):
          return []
  
      @classmethod
      def provides(cls):
          return ['max_z', 'min_z', 'range_z']
  
      def extract(self, source_point_cloud, neighborhood, target_point_cloud, target_index, volume_description):
          if neighborhood:
              z = source_point_cloud[point][self.DATA_KEY]['data'][neighborhood]
              max_z = np.max(z) if len(z) > 0 else self.DEFAULT_MAX
              min_z = np.min(z) if len(z) > 0 else self.DEFAULT_MIN
              range_z = max_z - min_z
          else:
              max_z = min_z = range_z = np.NaN
          return max_z, min_z, range_z
  
subject: update comment and clean formatting