code: def _copy(query_dict):
      
  
      memo = { }
  
      result = query_dict.__class__('',
          encoding=query_dict.encoding,
          mutable=True)
  
      memo[id(query_dict)] = result
  
      for key, value in dict.items(query_dict):
          dict.__setitem__(result,
              copy.deepcopy(key, memo),
              copy.deepcopy(value, memo))
  
      return result
docs: Return a mutable copy of `query_dict`. This is a workaround to
      Django bug #13572, which prevents QueryDict.copy from working.