def __delattr__(self, item):
     if hasattr(self, '_fields') and item in self._fields:
         del self[item]
     else:
         return Document.__delattr__(self, item)
 def __delattr__(self, item):
     if hasattr(self, '_fields') and item in self._fields:
         del self[item]
     else:
         return Document.__delattr__(self, item)