def subset(self, a, b):
        for x in a:
            if x not in b:
                return 0
        return 1
Takes a header key (i.e., "Host" in "Host: www.google.com",
dataset/ETHPy150Open smurfix/yapps/yapps/parsetree.py/Generator.subset--crossover with--dataset/ETHPy150Open catalyst256/gobbler/gobbler/layers/http.py/_canonicalize_header