code: def format(self):
          
          if self.dynamic_version_of is not None:
              return self.dynamic_version_of.format
  
          if not self._format:
              self._format = '%s_%%s' % self.name
          return self._format
docs: Return the format used to create the name of a variation of the current
          dynamic field. Use a default one ('fieldname_%s') if not set when the
          field was initialized