docs: function pathToRegexp (path, keys, options) {
  	  keys = keys || []
  	
  	  if (!isarray(keys)) {
  	    options = /** @type {!Object} */ (keys)
  	    keys = []
  	  } else if (!options) {
  	    options = {}
  	  }
  	
  	  if (path instanceof RegExp) {
  	    return regexpToRegexp(path, /** @type {!Array} */ (keys))
  	  }
  	
  	  if (isarray(path)) {
  	    return arrayToRegexp(/** @type {!Array} */ (path), /** @type {!Array} */ (keys), options)
  	  }
  	
  	  return stringToRegexp(/** @type {string} */ (path), /** @type {!Array} */ (keys), options)
  	}