Raise an error if the search is invalid for one of the following reasons:
* It contains multiple conflicting order: metatags (e.g. `order:score order:favcount` or `ordfav:a ordfav:b`).
* It contains a metatag that can't be used more than once: (e.g. `limit:5 limit:10`, `random:5 random:10`).
* It contains a metatag that can't be negated (e.g. `-order:score`, `-limit:20`, or `-random:20`).
* It contains a metatag that can't be used in an OR clause (e.g. ` touhou or order:score`, `touhou or limit:20`, `touhou or random:20`).
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