def __call__(self, *args, **kwargs):
        """Act like a function and enforce the contract that
        setting the chunksize takes only one integer input.
        """
        if len(args) != 1 or kwargs or not isinstance(args[0], int):
            raise ValueError(
                "parallel_chunksize takes only a " "single integer argument."
            )

        self.chunksize = args[0]
        return self
Act like a function and enforce the contract that
        setting the chunksize takes only one integer input.
        
numba/core/withcontexts.py