code: function(from, to) {
  		var path;
  		bfs(from || "es6", formatsTransformsGraph, function(cur) {
  			if (cur.node === to) {
  				path = cur.path;
  				return false;
  			}
  		});
  		return path;
  	}
docs: Whether it's possible to transform the source format to the dest format
  @param {string} from The format of the source, e.g: "es6"
  @parem {string} to the format of the output code, e.g: "amd"
  @return {?Array} The "path" of formats needed to transform
  from the source code to the dest format