SharePoint sp.taxonomy.js Term.getTerms not Working

A while back I worked on a small library with the SharePoint Online’s taxonomy, building the tree structure, and filtering the taxonomy data from SharePoint using JavaScript.

While most of the information can be found at SP.Taxonomy.js namespace in MSDN¬†and many resources online. But I’m struggling with one particular method of Term, according to the MSDN, the function to search for a term under a term will be

SP.Taxonomy.Term.getTerms(termLabel, lcid, defaultLabelOnly, stringMatchOption, resultCollectionSize, trimUnavailable)

This is different than searching for a term under the term store or term set level, which need to use the SP.Taxonomy.LabelMatchInformation for the request. So the code for searching for term in a term will look something like this:

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