def add_walls(self, method, **kwargs):
        """add wall to environment

        Parameters
        ----------
        method: str
            can be 'random' or 'custom'
            if method is 'random', then kwargs["n"] is a int
            if method is 'custom', then kwargs["pos"] is a list of coordination

        Examples
        --------
        # add 1000 walls randomly
        >>> env.add_walls(method="random", n=1000)

        # add 3 walls to (1,2), (4,5) and (9, 8) in map
        >>> env.add_walls(method="custom", pos=[(1,2), (4,5), (9,8)])
        """
        # handle = -1 for walls
        kwargs["dir"] = 0
        self.add_agents(-1, method, **kwargs)
add wall to environment

        Parameters
        ----------
        method: str
            can be 'random' or 'custom'
            if method is 'random', then kwargs["n"] is a int
            if method is 'custom', then kwargs["pos"] is a list of coordination

        Examples
        --------
        # add 1000 walls randomly
        >>> env.add_walls(method="random", n=1000)

        # add 3 walls to (1,2), (4,5) and (9, 8) in map
        >>> env.add_walls(method="custom", pos=[(1,2), (4,5), (9,8)])
        
python/magent/gridworld.py