function _parseArguments(options, callback) {
  if (typeof options == 'function') {
    return [callback || {}, options];
  }

  if (_isUndefined(options)) {
    return [{}, callback];
  }

  return [options, callback];
}
Parses the function arguments.

This function helps to have optional arguments.

@param {(Options|Function)} options
@param {Function} callback
@returns {Array} parsed arguments
@private