What is the meaning of the message "Pyomo: DEPRECATED: Using __getitem__ to retrieve a value from its ordered position and return it as a set is no longer recommended"?

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The message means that the code is using a method (__getitem__) that is no longer recommended for retrieving a value from its ordered position and returning it as a set in Pyomo. This method is deprecated, which means that it may not be supported in future versions of Pyomo and may cause errors. It is recommended to use alternative methods instead.