It naturally deals with complex expressions such as OR, AND, etc.
So there is no need to parse the string query anymore.
https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-simple-query-string-query.html

A list of values for a parameter is obtained with a URL
such as &param=value1&param=value2
The returned dictionary will be:
{ param : [value1, value2]}