Classifies a single search term as a plain string, a CAS number, a SMILES string, or a chemical formula. Detection is heuristic and intended only to colorize the search box — it never changes what is searched. Phrases (anything containing whitespace) are always plain strings, since CAS/SMILES/formula tokens are contiguous.
The kind of thing a single search term looks like. Used purely to colorize the search box — it does not change search behavior.