code: def get(self, key):
          
  
          self.maybe_clean()
          v = self.data.get(key)
          if v is None or v.expiration <= time.time():
              return None
          return v
docs: Get the answer associated with I{key}.  Returns None if
          no answer is cached for the key.
          @param key: the key
          @type key: (dns.name.Name, int, int) tuple whose values are the
          query name, rdtype, and rdclass.
          @rtype: dns.resolver.Answer object or None