old_contents: class Base(dict):
  
      def _get_property(self, name):
          """Return the named property from dictionary values."""
          if not self[name]:
              return None
          return self[name]
  
new_contents: class Base(dict):
  
      def _get_property(self, name):
          """Return the named property from dictionary values."""
          if name not in self:
              return None
          return self[name]
  
subject: Make _get_property to return none when name does not exist