def __init__(self, authorities=None, caches=None, clients=None, verbose=0):
        """
        @param authorities: Resolvers which provide authoritative answers.
        @type authorities: L{list} of L{IResolver} providers

        @param caches: Resolvers which provide cached non-authoritative
            answers. The first cache instance is assigned to
            C{DNSServerFactory.cache} and its C{cacheResult} method will be
            called when a response is received from one of C{clients}.
        @type caches: L{list} of L{Cache<twisted.names.cache.CacheResolver>} instances

        @param clients: Resolvers which are capable of performing recursive DNS
            lookups.
        @type clients: L{list} of L{IResolver} providers

        @param verbose: An integer controlling the verbosity of logging of
            queries and responses. Default is C{0} which means no logging. Set
            to C{2} to enable logging of full query and response messages.
        @type verbose: L{int}
        """
        resolvers = []
        if authorities is not None:
            resolvers.extend(authorities)
        if caches is not None:
            resolvers.extend(caches)
        if clients is not None:
            resolvers.extend(clients)

        self.canRecurse = not not clients
        self.resolver = resolve.ResolverChain(resolvers)
        self.verbose = verbose
        if caches:
            self.cache = caches[-1]
        self.connections = []

        @param authorities: Resolvers which provide authoritative answers.
        @type authorities: L{list} of L{IResolver} providers

        @param caches: Resolvers which provide cached non-authoritative
            answers. The first cache instance is assigned to
            C{DNSServerFactory.cache} and its C{cacheResult} method will be
            called when a response is received from one of C{clients}.
        @type caches: L{list} of L{Cache<twisted.names.cache.CacheResolver>} instances

        @param clients: Resolvers which are capable of performing recursive DNS
            lookups.
        @type clients: L{list} of L{IResolver} providers

        @param verbose: An integer controlling the verbosity of logging of
            queries and responses. Default is C{0} which means no logging. Set
            to C{2} to enable logging of full query and response messages.
        @type verbose: L{int}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/server.py