docs: def local_port_range(self):
          """Tuple of (low_port, high_port) reflecting the local port range
          assigned to outbound connections. We use this as part of a heuristic
          to determine whether a connection is inbound or outbound.
          """
          if self._local_port_range is None:
              with open('/proc/sys/net/ipv4/ip_local_port_range', 'r') as f:
                  self._local_port_range = tuple(map(int, f.read().split('\t')))
          return self._local_port_range