'Given a project_id, return a list of routers that are all in
the given project.  Returns empty list if the project_id provided
doesn\'t evaluate to True.'

def get_routers_in_project(self, project_id):

    if project_id:
        return [ri for ri in self._router_info.values() if (ri.router['project_id'] == project_id)]
    else:
        return []
