code: function stringify (data) {
    var str;
    if (typeof data !== OBJECT) { return data; }
    str = data.x + ' ' + data.y;
    if (data.z != null) { str += ' ' + data.z; }
    if (data.w != null) { str += ' ' + data.w; }
    return str;
  }
docs: Stringify coordinates from an object with keys [x y z].
  Example: {x: 3, y: 10, z: -5} to "3 10 -5".
  
  @param {object|string} data - An object with keys [x y z].
  @returns {string} An "x y z" string.