def METHOD_NAME(self, out_fname, coords=None):
    """Writing vertex coordinates as a .ply file using plyfile"""
    if coords is None:
        coords = self.vertices
    tweaked_array = np.array(
        list(zip(coords[:, 0], coords[:, 1], coords[:, 2])),
        dtype=[('x', 'f4'), ('y', 'f4'), ('z', 'f4')])
    vertex_element = plyfile.PlyElement.describe(tweaked_array, "vertex")
    if not os.path.exists(os.path.dirname(out_fname)):
        os.makedirs(os.path.dirname(out_fname))
    plyfile.PlyData([vertex_element]).write(out_fname)