def _sum_size(self, equiv_set, sizes):
        """Return the sum of the given list of sizes if they are all equivalent
        to some constant, or None otherwise.
        """
        s = 0
        for size in sizes:
            n = equiv_set.get_equiv_const(size)
            if n is None:
                return None
            else:
                s += n
        return s
Return the sum of the given list of sizes if they are all equivalent
        to some constant, or None otherwise.
        
numba/parfors/array_analysis.py