old_contents: from mongo import Base, dictproperty
  from changeset import Revisioned
  
  class Dataset(Revisioned):
  
      id = dictproperty('_id')
      name = dictproperty('name')
      label = dictproperty('label')
      description = dictproperty('description')
      currency = dictproperty('currency')
      entry_custom_html = dictproperty('entry_custom_html')
  
      def get_regions(self):
          if not "regions" in self:
              self["regions"] = []
          return self["regions"]
  
      def add_region(self, region):
          regions = set(self.get_regions())
          regions.add(region)
          self["regions"] = list(regions)
  
      @classmethod
      def find_by_region(cls, region):
          return Dataset.find({"regions": region})
  
      @classmethod
      def distinct_regions(cls):
          return Dataset.c.distinct("regions")
  
new_contents: from mongo import dictproperty
  from changeset import Revisioned
  
  class Dataset(Revisioned):
  
      id = dictproperty('_id')
      name = dictproperty('name')
      label = dictproperty('label')
      description = dictproperty('description')
      currency = dictproperty('currency')
      entry_custom_html = dictproperty('entry_custom_html')
  
      def get_regions(self):
          if not "regions" in self:
              self["regions"] = []
          return self["regions"]
  
      def add_region(self, region):
          regions = set(self.get_regions())
          regions.add(region)
          self["regions"] = list(regions)
  
      @classmethod
      def find_by_region(cls, region):
          return Dataset.find({"regions": region})
  
      @classmethod
      def distinct_regions(cls):
          return Dataset.c.distinct("regions")
  
subject: Remove unused import