convert
Converts the given romaji input to Japanese using the API client. Utilizes a word-level cache to store and retrieve previous conversion results. Each word is cached separately to improve cache hit rate.
Step 1: Romanji -> Hiragana (using KanaConverter) Step 2: Hiragana -> Kanji/Kana (using Google IME API)
Return
The converted Japanese string, or null if the input contains non-romaji characters.
Parameters
input
The romaji string to convert.
Throws
if the conversion process encounters an error.