docs: def select(sockets, remain=None):
          """This function is called during sendrecv() routine to select
          the available sockets.
          """
          if remain is not None:
              max_timeout = remain / len(sockets)
              for s in sockets:
                  if s.timeout > max_timeout:
                      s.timeout = max_timeout
  
          # python-can sockets aren't selectable, so we return all of them
          # sockets, None (means use the socket's recv() )
          return sockets, None