docs: def db(cls, path=None):
          """
          Returns a pymongo Collection object from the current database connection.
          If the database connection is in test mode, collection will be in the
          test database.
          
          @param path: if is None, the PATH attribute of the current class is used;
              if is not None, this is used instead
          
          @raise Exception: if neither cls.PATH or path are valid
          """
          if cls.PATH is None and path is None:
              raise Exception("No database specified")
          if path is None:
              path = cls.PATH
          if "." not in path:
              raise Exception(('invalid path "%s"; database paths must be ' +
                               'of the form "database.collection"') % (path,))
          if CONNECTION.test_mode:
              return CONNECTION.get_connection()[TEST_DATABASE_NAME][path]
          (db, coll) = path.split('.', 1)
          return CONNECTION.get_connection()[db][coll]