[Python] NameError: name 'List' is not defined

I'm really unsure why this isn't working. Here is the important part of the code (it's from a leetcode challenge). The first line throws the NameError.

def totalFruit(self, tree: List[int]) -> int:
pass


If I try importing List first I get an error No module named 'List'. I'm using Python 3.7.3 from Anaconda.

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