code: def attributes(self):
          
          if not self._attribute_pages:
              self.fetch_attributes()
          result = {}
          for page in self._attribute_pages.values():
              result.update(page.attributes)
          return result
docs: A dictionary mapping names of attributes to BiomartAttribute instances.
  
          This causes overwriting errors if there are diffferent pages which use
          the same attribute names, but is kept for backward compatibility.