code: def load_source_vocabs(folder: str) -> List[Vocab]:
      
      return [vocab_from_json(os.path.join(folder, fname)) for fname in
              sorted([f for f in os.listdir(folder) if f.startswith(C.VOCAB_SRC_PREFIX)])]
docs: Loads source vocabularies from folder. The first element in the list is the primary source vocabulary.
      Other elements correspond to optional additional source factor vocabularies found in folder.
  
      :param folder: Source folder.
      :return: List of vocabularies.