I have a list containing multiple lists as its elements

eg: [[1,2,3,4],[4,5,6,7]]

If I use the built in set function to remove duplicates from this list, I get the error

TypeError: unhashable type: 'list'

The code I'm using is

TopP = sorted(set(TopP),reverse=True)

Where TopP is a list just like in the e.g. Above

Is this usage of set() wrong? Is there any other way in which I can sort the above list?

python list duplicates
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