Return the type of the version control backend if found at given
        location, e.g. vcs.get_backend_type('/path/to/vcs/checkout')

def get_backend_type(self, location):
        # type: (str) -> Optional[Type[VersionControl]]
        """
        Return the type of the version control backend if found at given
        location, e.g. vcs.get_backend_type('/path/to/vcs/checkout')
        """
        for vc_type in self._registry.values():
            if vc_type.controls_location(location):
                logger.debug('Determine that %s uses VCS: %s',
                             location, vc_type.name)
                return vc_type
        return None