def add_mountains(self):
        """
        instead of the add_blocks function which was to produce
        line shaped walls for blocking path finding agents, this
        function creates more natural looking blocking areas like
        mountains
        """
        from noise import pnoise2
        import random
        random.seed()
        octaves = (random.random() * 0.5) + 0.5
        freq = 17.0 * octaves  # 
        for y in range(self.grd.grid_height - 1):
            for x in range(self.grd.grid_width - 1):
                pixel = self.grd.get_tile(y,x)
                if pixel == 'X':     # denoise blocks of mountains
                    n = int(pnoise2(x/freq, y / freq, 1)*11+5)
                    if n < 1:
                        self.grd.set_tile(y, x, '#')
instead of the add_blocks function which was to produce
        line shaped walls for blocking path finding agents, this
        function creates more natural looking blocking areas like
        mountains