code: def _append_to(self, field, element):
          
          if element not in EMPTIES:
              self.obj.setdefault(field, [])
              self.obj.get(field).append(element)
docs: Append the ``element`` to the ``field`` of the record.
  
          This method is smart: it does nothing if ``element`` is empty and
          creates ``field`` if it does not exit yet.
  
          Args:
              :param field: the name of the field of the record to append to
              :type field: string
              :param element: the element to append