Cannot use this for japanese text

[MARUD84]

Dear Tim Schopf, Thank you for your effort in creating this library. It has been really useful for extracting key phrases for English, German and Chinese text, but i am having trouble applying it to Japanese text.
As suggested i have changed the spacy_pipeline to ja_core_news_sm and have a list of Japanese stop words, but i am getting the following error:
ValueError: Empty keyphrases. Perhaps the documents do not contain keyphrases that match the 'pos_pattern' parameter or only contain stop words.
Do you happen to know why this might be?