code: def find_usage(self):
          
          logger.debug("Checking usage for service %s", self.service_name)
          self.connect()
          for lim in self.limits.values():
              lim._reset_usage()
          self._find_usage_vpcs()
          subnet_to_az = self._find_usage_subnets()
          self._find_usage_ACLs()
          self._find_usage_route_tables()
          self._find_usage_gateways()
          self._find_usage_nat_gateways(subnet_to_az)
          self._find_usages_vpn_gateways()
          self._find_usage_network_interfaces()
          self._have_usage = True
          logger.debug("Done checking usage.")
docs: Determine the current usage for each limit of this service,
          and update corresponding Limit via
          :py:meth:`~.AwsLimit._add_current_usage`.