Base class for all FDSN routers.
The ObsPy Development Team (firstname.lastname@example.org) Celso G Reyes, 2017 IRIS-DMC
GNU Lesser General Public License, Version 3 (https://www.gnu.org/copyleft/lesser.html)
Helper function to get the correct routing instance.
Private functions are mainly for internal/developer use and their API might change without notice.